Method for recycling and converting waste lithium cobalt oxide positive electrode material into high-performance lithium supplement agent, high-performance lithium supplement agent and application of high-performance lithium supplement agent

Abstract

The invention relates to a method for recycling and converting a waste lithium cobalt oxide positive electrode material into a high-performance lithium supplement agent, the high-performance lithium supplement agent and application of the high-performance lithium supplement agent. The method comprises the following steps: converting the waste lithium cobalt oxide positive electrode material (LiCoO2) into a Li6CoO4 material with an antifluorite structure; the conversion process comprises adding a certain proportion of lithium source and carrying out heat treatment, and the finally obtained antifluorite structure Li6CoO4 can be used as a lithium supplement additive to make up the loss of irreversible active lithium in a lithium ion battery, so that the energy density and the cycle life of the battery are effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion battery recycling, and relates to a method for recycling waste lithium cobalt oxide positive electrode materials into a high-performance lithium supplement agent, a high-performance lithium supplement agent and an application thereof. Background Art

[0002] As society's demand for energy storage continues to grow, more and more lithium-ion batteries are widely put on the market. However, the battery life is limited, and the speed of electronic product replacement is fast, which leads to the generation of a large number of discarded lithium-ion batteries. According to forecasts, more than 100,000 tons of scrapped lithium-ion batteries are generated from electronic devices worldwide each year, among which lithium cobalt oxide (LCO) occupies a dominant position in portable electronic devices due to its excellent performance, such as high energy density and stability. The retirement and disposal of a large number of lithium cobalt oxide batteries have brought huge environmental pressure and resource problems. On the one hand, cobalt, as a heavy metal, can cause great harm to the environment and human health. On the other hand, metals such as cobalt and lithium have very high economic value as scarce strategic resources. It is of great significance to efficiently, economically and environmentally friendly recover the lithium and cobalt resources in the waste lithium cobalt oxide positive electrode, which can not only bring extremely high economic benefits and save resources, but also conform to the concept of green circulation and sustainable development.

[0003] At present, the recycling of waste LCO batteries mainly includes pyrometallurgy, hydrometallurgy and direct repair methods. Pyrometallurgy occupies a dominant position in the industry because it does not need to classify and pre-treat waste batteries and can achieve batch processing. For example, patent CN114317977A pyrolyzes polyvinyl chloride and waste lithium cobalt oxide in an inert atmosphere to obtain a co-pyrolysis product containing lithium and cobalt. However, this method consumes a lot of energy, and the harmful gases and pollutants generated during the recovery process will have a serious impact on the environment, and the lithium element will be lost in the slag, and the recovery efficiency is low. Hydrometallurgy has advantages in recovery efficiency, energy consumption and product purity. For example, hydrochloric acid or sulfuric acid is used as a leaching agent to extract cobalt and lithium from waste LCO, and then solvent extraction and electrolysis processes are used to separate cobalt and lithium from the leachate, which can achieve higher recovery efficiency and product purity (CN116354408A, CN118125510A). However, due to the large liquid / solid ratio of the leaching process, the burden of wastewater treatment is increased, resulting in great challenges in these methods in terms of economy and environmental friendliness.

[0004] Compared with pyrometallurgy and hydrometallurgy, direct repair methods have greater application potential. This strategy has been widely used in the recycling of waste lithium iron phosphate (LFP) batteries (CN111792633A, CN117401662A). Due to the stable olivine structure, the degradation of the LFP cathode is mainly due to the loss of active lithium and slight Li / Fe anti-site defects. Direct regeneration of waste LFP can be easily achieved through lithium supplementation and sintering. However, for layered materials such as LCO and NCM, long-term cycling will not only deplete the active lithium, but also induce severe irreversible structural damage, generating spinel phase Co3O4 on the surface. These irreversible damages pose great challenges to the repair of LCO. Patents CN114597532 A and CN114426312A use solid-state sintering to directly repair waste LCO cathodes, rebuilding their lattice structure to restore their electrochemical properties. However, for LCO cathodes with severe structural damage, this method has limited repair effects and cannot completely restore the structural damage and phase change of LCO. If it is reused as a new cathode material, its cycle performance is worrying. On the other hand, the existing direct recycling method is difficult to universally recycle LCO with different degrees of failure. It is still limited to limited laboratory-scale operations and has not yet been widely used. Therefore, a technology that can efficiently recycle without considering the degree of electrode damage is needed. Summary of the invention

[0005] The purpose of the present invention is to provide a method for recycling waste lithium cobalt oxide positive electrode materials into a high-performance lithium supplement, a high-performance lithium supplement and its application, which can quickly, efficiently and with low energy consumption and can indiscriminately recycle waste LCO positive electrodes into lithium supplements with excellent performance.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] In one aspect, the present invention provides a method for recycling waste lithium cobalt oxide positive electrode materials into a high-performance lithium supplement, comprising the following steps:

[0008] (1) Pretreatment of waste LCO batteries: The retired LCO batteries are discharged and then disassembled under inert atmosphere to obtain LCO positive electrode sheets, which are cleaned and dried to remove residual electrolyte solvent and lithium salt on the surface, and heat treated to collect the failed LCO positive electrode powder that falls off the positive aluminum foil current collector;

[0009] (2) Synthesis of Li6CoO4 by heat treatment: The collected failed LCO positive electrode powder, lithium source and carbon source are mixed evenly, pressed into tablets, and then rapidly sintered to obtain Li6CoO4 material with an inverse fluorite structure, which is the high-performance lithium supplement.

[0010] Furthermore, in step (1), the residual capacity of the failed lithium cobalt oxide positive electrode (i.e., failed LCO positive electrode powder) is 10-40% of the initial capacity.

[0011] Furthermore, in step (1), the discharge treatment process is specifically as follows: firstly, the waste LCO battery is discharged to 2V, and then it is immersed in a 0.8-1.2 mol / L NaCl aqueous solution to discharge it completely, and the immersion time is 2-12 hours.

[0012] Furthermore, in step (1), the heat treatment temperature is 400-500° C., the time is 2-3 hours, and the atmosphere is air or oxygen.

[0013] Furthermore, the inert atmosphere in step (1) is argon or the like.

[0014] Further, in step (2), taking Li2O as an example, the reaction between the spent LCO positive electrode powder, the lithium source and the carbon source is: The overall reaction equation is: Determine the ratio of Li and Co in the waste LCO according to ICP, and then adjust the amount of Li source and C source added according to the above formula. The Li source can also be replaced with LiOH and Li2CO3 to ensure that the molar ratio of Li and Co in the final product is 6:1.

[0015] Specifically, the amount of added spent LCO cathode powder and lithium source satisfies: the molar ratio of Li to Co is 6:1;

[0016] The amount of carbon source added satisfies that the spent LCO positive electrode powder and the lithium source can fully react to generate Li6CoO4 and CO2.

[0017] Furthermore, in step (2), the lithium source is one or more of Li2O, LiOH and Li2CO3.

[0018] Furthermore, in step (2), the carbon source is one or more of carbon black, graphite, glucose or starch.

[0019] Furthermore, in step (2), the mixing method is mortar grinding or mechanical ball milling, the ball milling rate is 200-600 r / min, and the ball milling time is 2-8 h.

[0020] Furthermore, in step (2), the heat treatment method can be selected, including but not limited to rapid sintering methods such as tube furnace sintering, Joule heat heating, microwave heating and plasma heating.

[0021] Preferably, in step (2), the rapid sintering treatment adopts Joule heat rapid sintering, the temperature is 800-1200° C., the heating time is 5-20 s, and the atmosphere is vacuum or inert atmosphere.

[0022] Preferably, in step (2), the sintering temperature in the tubular furnace is 700-900°C, the heating time is 2-12h, and the atmosphere is an inert gas such as Ar and N2.

[0023] Preferably, the Joule heat fast burning temperature in step (2) is 800-1200° C., the heating time is 5-20 s, and the atmosphere is vacuum or an inert gas such as Ar, N2, etc.

[0024] Preferably, the power of the microwave rapid heating in step (2) is 900-1500w, and the microwave treatment time is 10-30s.

[0025] In a second aspect, the present invention provides a high-performance lithium supplement, which is prepared by the method described above.

[0026] In a third aspect, the present invention provides an application of a high-performance lithium supplement agent, wherein the high-performance lithium supplement agent is added to the positive electrode slurry during the positive electrode homogenization process to supplement the positive electrode lithium.

[0027] Furthermore, the solid content of the positive electrode slurry is 30-35%.

[0028] Furthermore, the positive electrode slurry is prepared from a positive electrode active material, a conductive agent, a binder, a lithium supplement agent and a solvent, and has a solid content of 30-35%. The mass ratio of the positive electrode active material, the conductive agent, the binder and the lithium supplement agent is (76-95): (2-10): (3-10): (2-5).

[0029] Furthermore, the positive electrode active material is one or more of lithium iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium manganese iron phosphate.

[0030] Furthermore, the conductive agent is selected from one or more of Super-P, Ketjen black, mesoporous carbon, carbon nanotubes and graphene.

[0031] Furthermore, the binder is selected from one or more of polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber and polyethyl methacrylate.

[0032] Furthermore, the solvent is selected from one or more of N-methylpyrrolidone and dimethylformamide.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] (1) Efficient recycling of waste LCO cathode

[0035] The present invention adopts Joule heat rapid sintering process, uses current pulse to generate Joule heat to quickly heat up the sample, and directly converts the waste LCO positive electrode material into Li6CoO4 in a short time. This process hardly causes loss of Li and Co, and the recovery efficiency of Li and Co resources can be close to 100%.

[0036] (2) It can achieve indiscriminate recycling regardless of the damage degree of LCO and adapt to battery materials with different failure degrees

[0037] The present invention innovatively bypasses the traditional regeneration and repair, and does not need to repair LCO back to its original layered structure. It can achieve indiscriminate direct conversion regardless of the degree of electrode damage, and completely converts waste LCO with severe structural damage into Li6CoO4. Therefore, the method has good adaptability and can be widely used in the recycling of batteries with different degrees of failure.

[0038] (3) Li6CoO4 as an efficient lithium supplement to improve battery performance

[0039] The present invention uses the converted Li6CoO4 as a lithium supplement in lithium-ion batteries, providing an irreversible capacity of more than 700mAh / g, significantly improving the battery capacity and cycle life. It is completely decomposed in the first cycle and loses its electrochemical activity in subsequent cycles. It can be used with new positive electrode materials without considering the cycle performance of the recycled product itself.

[0040] (4) Simple operation process and high economic benefits

[0041] The present invention avoids high-temperature smelting, chemical solvents and wastewater treatment in the traditional recycling process, simplifies the recycling process, saves energy consumption and raw material costs. It not only improves the recycling efficiency, but also has good economic benefits. The regenerated Li6CoO4 has higher economic value and has obvious advantages over commercialized positive lithium supplements such as lithium ferrite and lithium nickel oxide. Therefore, it has good application prospects.

[0042] (5) Green and environmentally friendly, no harmful waste gas emissions

[0043] The present invention is also environmentally friendly, and the recycling process does not require the use of any harmful chemicals, and does not generate toxic waste gas and waste water, thus meeting the requirements of green environmental protection and reducing the environmental pollution that may be caused by traditional methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The XRD pattern of the waste LCO used in Example 1 of the present invention;

[0045] Figure 2 The XRD spectrum of Li6CoO4 converted from waste LCO in Example 3 of the present invention;

[0046] Figure 3 This is the first cycle charge and discharge curve of Li6CoO4 in Example 3;

[0047] Figure 4 It is a comparison diagram of the first cycle charge and discharge curves of the lithium ion batteries in Example 12 and Comparative Example 1;

[0048] Figure 5 It is a comparison chart of the cycle performance of the lithium ion batteries in Example 12 and Comparative Example 1. DETAILED DESCRIPTION

[0049] In order to solve the problems of high energy consumption, serious pollution and low recovery efficiency in existing pyrometallurgical and hydrometallurgical recovery technologies, as well as the problem that existing direct recovery methods are difficult to completely repair highly damaged LCO positive electrodes, the present invention provides a method for recycling waste lithium cobalt oxide positive electrode materials into high-performance lithium supplement agents, which avoids the complexity of structural damage of waste LCO and indiscriminately converts it into a lithium supplement material with excellent performance, which is used as a positive electrode additive and put into a new round of use, and is used with new positive electrode materials without worrying about its own cycle performance.

[0050] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0051] In the following examples, unless otherwise specified, raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0052] Embodiment 1:

[0053] A method for converting spent LCO into a Li6CoO4 lithium supplement comprises the following steps:

[0054] (1) Pretreatment of used LCO batteries

[0055] The retired LCO battery was discharged to 2V and then placed in 1mol L -1 The battery was completely discharged in a NaCl solution, and then disassembled in an argon-filled glove box to obtain the waste LCO positive electrode sheet, which was washed with dimethyl carbonate (DMC) to remove the residual electrolyte solvent and lithium salt on the surface. It was then transferred to a muffle furnace and heat treated at 500°C for 3h to remove the residual carbon and PVDF binder. After treatment, the positive active material fell off the aluminum foil current collector, and the failed LCO positive electrode material was collected, with a residual capacity of 40% of the initial capacity.

[0056] (2) Rapid sintering of Li6CoO4 using Joule heat

[0057] The ICP composition analysis of the failed LCO positive electrode material was carried out to determine the ratio of Li and Co. According to the reaction equation: Li 0.4 CoO2+2.8Li2O+0.4C→Li6CoO4+0.4CO2, determine the ratio of adding Li2O and C reducing agent. Take 0.312g of waste LCO (i.e. the failed LCO positive electrode material obtained above), 0.28g of Li2O, and 0.016g of carbon black and grind them evenly in a mortar. Use a powder tablet press to press the mixture into tablets, put it into a Joule heat fast burning device, set the current pulse parameters under argon atmosphere, heat the material to 800℃, and continue heating for 10 seconds. During this process, the crystal structure of LCO changes from a layered structure to an anti-fluorite structure of Li6CoO4.

[0058] Embodiment 2:

[0059] A method for converting spent LCO into a Li6CoO4 lithium supplement comprises the following steps:

[0060] (1) The waste LCO battery was pretreated in the same manner as in Example 1 to obtain waste LCO positive electrode powder, the residual capacity of which was 40% of the initial capacity.

[0061] (2) Li6CoO4 was synthesized by rapid sintering using Joule heat. The difference from Example 1 was that the sintering temperature was 900°C and the heating duration was 10 seconds.

[0062] Embodiment 3:

[0063] A method for converting spent LCO into a Li6CoO4 lithium supplement comprises the following steps:

[0064] (1) The waste LCO battery was pretreated in the same manner as in Example 1 to obtain waste LCO positive electrode powder, the residual capacity of which was 40% of the initial capacity.

[0065] (2) Li6CoO4 was synthesized by rapid sintering using Joule heat. The difference from Example 1 was that the sintering temperature was 1000°C and the heating duration was 10 seconds.

[0066] Embodiment 4:

[0067] A method for converting spent LCO into a Li6CoO4 lithium supplement comprises the following steps:

[0068] (1) The waste LCO battery was pretreated in the same manner as in Example 1 to obtain waste LCO positive electrode powder, the residual capacity of which was 40% of the initial capacity.

[0069] (2) Li6CoO4 was synthesized by rapid sintering using Joule heat. The difference from Example 1 was that the sintering temperature was 1100°C and the heating duration was 10 seconds.

[0070] Embodiment 5:

[0071] A method for converting spent LCO into a Li6CoO4 lithium supplement comprises the following steps:

[0072] (1) The waste LCO battery was pretreated in the same manner as in Example 1 to obtain waste LCO positive electrode powder, the residual capacity of which was 40% of the initial capacity.

[0073] (2) Li6CoO4 was synthesized by rapid sintering using Joule heat. The difference from Example 1 was that the sintering temperature was 1200°C and the heating duration was 10 seconds.

[0074] Embodiment 6:

[0075] A method for converting spent LCO into a Li6CoO4 lithium supplement comprises the following steps:

[0076] (1) The waste LCO battery was pretreated in the same manner as in Example 1 to obtain waste LCO positive electrode powder, the residual capacity of which was 40% of the initial capacity.

[0077] (2) Li6CoO4 was synthesized by rapid sintering using Joule heat. The difference from Example 1 was that the sintering temperature was 1000°C and the heating duration was 5 seconds.

[0078] Embodiment 7:

[0079] A method for converting spent LCO into a Li6CoO4 lithium supplement comprises the following steps:

[0080] (1) The waste LCO battery was pretreated in the same manner as in Example 1 to obtain waste LCO positive electrode powder, the residual capacity of which was 40% of the initial capacity.

[0081] (2) Li6CoO4 was synthesized by rapid sintering using Joule heat. The difference from Example 1 was that the sintering temperature was 1000°C and the heating duration was 20 seconds.

[0082] Figure 1The XRD spectrum of waste LCO is given, from which the presence of Co3O4 phase can be clearly seen, indicating that irreversible structural damage has occurred to LCO during the cycle. The heat treatment conditions of Examples 1-7 and the performance of the obtained Li6CoO4 are summarized in Table 1. As the sintering temperature increases, the conversion rate from LCO to Li6CoO4 gradually increases, and the first cycle charge capacity of the obtained product increases from 580mAh / g to more than 700mAh / g. Figure 2 The XRD spectrum of the product in Example 3 is displayed, and the results show that at 1000°C and a sintering time of 10 seconds, the diffraction peak corresponding to LCO completely disappears, and the waste LCO is completely converted into Li6CoO4. Figure 3 The first cycle charge-discharge curve of Li6CoO4 obtained in Example 3 is given. In the voltage range of 2.5-4.3V, the charging curve has two obvious platforms. Each Li6CoO4 molecule can contribute 5 active Li + The charging capacity exceeds 700mAh / g, while the discharge capacity is almost 0, making it an ideal lithium supplement material.

[0083] Embodiment 8:

[0084] A method for converting spent LCO into a Li6CoO4 lithium supplement comprises the following steps:

[0085] (1) The waste LCO battery was pretreated in the same manner as in Example 1 to obtain waste LCO positive electrode powder, the residual capacity of which was 20% of the initial capacity.

[0086] (2) The composition of the failed LCO was analyzed by ICP to determine the ratio of Li and Co, and the reaction equation was: Li 0.2 CoO2+2.9Li2O+0.45C→Li6CoO4+0.45CO2, determine the ratio of adding Li2O and C reducing agent. Li6CoO4 is synthesized by rapid sintering by Joule heat, the sintering temperature is 1000℃, and the heating duration is 10 seconds.

[0087] Embodiment 9:

[0088] A method for converting spent LCO into a Li6CoO4 lithium supplement comprises the following steps:

[0089] (1) The waste LCO battery was pretreated in the same manner as in Example 1 to obtain waste LCO positive electrode powder, the residual capacity of which was 10% of the initial capacity.

[0090] (2) The composition of the failed LCO was analyzed by ICP to determine the ratio of Li and Co, and the reaction equation was: Li 0.1CoO2+2.95Li2O+0.475C→Li6CoO4+0.475CO2, determine the ratio of adding Li2O and C reducing agent. Li6CoO4 is synthesized by rapid sintering by Joule heat, the sintering temperature is 1000℃, and the heating duration is 10 seconds.

[0091] Table 1 shows the first charge capacity of Li6CoO4 obtained in Example 3, Example 8 and Example 9. Although the structural damage of LCO in Examples 8 and 9 is more serious, there is no obvious difference in the charge capacity of the products recovered by this method, which shows that this method can be used to recycle LCO positive electrodes with different degrees of failure and has good universality.

[0092] Table 1

[0093]

[0094]

[0095] Embodiment 10:

[0096] A method for converting spent LCO into a Li6CoO4 lithium supplement comprises the following steps:

[0097] (1) The waste LCO battery was pretreated in the same manner as in Example 1 to obtain waste LCO positive electrode powder, the residual capacity of which was 40% of the initial capacity.

[0098] (2) Li6CoO4 was synthesized by sintering in a tubular furnace at a temperature of 700°C for 12 h in an Ar atmosphere.

[0099] Example 11: A method for converting spent LCO into a Li6CoO4 lithium supplement, comprising the following steps:

[0100] (1) The waste LCO battery was pretreated in the same manner as in Example 1 to obtain waste LCO positive electrode powder, the residual capacity of which was 40% of the initial capacity.

[0101] (2) Li6CoO4 was synthesized by microwave rapid heating method with microwave power of 900w and microwave treatment time of 20s.

[0102] Embodiment 12:

[0103] A method for preparing a positive electrode sheet and a full battery using Li6CoO4 for positive electrode lithium supplementation specifically comprises the following steps:

[0104] (1) Preparation of positive electrode sheet

[0105] Lithium iron phosphate positive electrode material (LFP), conductive agent Super-P, binder polyvinylidene fluoride (PVDF) and lithium supplement agent Li6CoO4 prepared in Example 3 were mixed in a mass ratio of 0.776:0.1:0.1:0.024, dispersed in N-methylpyrrolidone (NMP) solvent and stirred with a homogenizer, and the obtained positive electrode slurry was coated on an aluminum foil positive electrode collector, and cut to obtain a positive electrode sheet after drying;

[0106] (2) Preparation of negative electrode sheet

[0107] Graphite (Gr), conductive agent Super-P, and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 90:5:5 and dispersed in NMP solvent to prepare a negative electrode slurry, which was then coated on a copper foil current collector and cut to obtain a negative electrode sheet after drying;

[0108] (3) Assembly of the full battery

[0109] After stacking the positive electrode sheet obtained in step (1), the PP separator, and the negative electrode sheet obtained in step (2), an electrolyte (1 mol / L LiPF6 EC:DMC=3:7 2% VC) was injected to assemble a button cell. A constant current charge and discharge test was then performed.

[0110] Embodiment 13:

[0111] A method for preparing a positive electrode sheet and a full battery using Li6CoO4 for positive electrode lithium supplementation specifically comprises the following steps:

[0112] (1) Preparation of positive electrode sheet

[0113] The lithium cobalt oxide positive electrode material (LCO), the conductive agent Super-P, the binder polyvinylidene fluoride (PVDF) and the lithium supplement agent Li6CoO4 prepared in Example 3 were mixed in a mass ratio of 0.776:1:1:0.024, dispersed in N-methylpyrrolidone (NMP) solvent and stirred with a homogenizer, and the obtained positive electrode slurry was coated on an aluminum foil positive electrode collector, and cut to obtain a positive electrode sheet after drying;

[0114] (2) Preparation of negative electrode sheet

[0115] Graphite (Gr), conductive agent Super-P, and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 90:5:5 and dispersed in NMP solvent to prepare a negative electrode slurry, which was then coated on a copper foil current collector and cut to obtain a negative electrode sheet after drying;

[0116] (3) Assembly of the full battery

[0117] After stacking the positive electrode sheet obtained in step (1), the PP separator, and the negative electrode sheet obtained in step (2), an electrolyte (1 mol / L LiPF6 EC:DMC=3:7 2% VC) was injected to assemble a button cell. A constant current charge and discharge test was then performed.

[0118] Embodiment 14:

[0119] A method for preparing a positive electrode sheet and a full battery using Li6CoO4 for positive electrode lithium supplementation specifically comprises the following steps:

[0120] (1) Preparation of positive electrode sheet

[0121] The nickel cobalt manganese oxide lithium positive electrode material (NCM811), the conductive agent Super-P, the binder polyvinylidene fluoride (PVDF) and the lithium supplement agent Li6CoO4 prepared in Example 3 were mixed in a mass ratio of 0.76:1:1:0.04, dispersed in N-methylpyrrolidone (NMP) solvent and stirred with a homogenizer, and the obtained positive electrode slurry was coated on an aluminum foil positive electrode collector, and cut to obtain a positive electrode sheet after drying;

[0122] (2) Preparation of negative electrode sheet

[0123] Silicon carbon (Si / C), conductive agent Super-P, and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 90:5:5 and dispersed in NMP solvent to prepare negative electrode slurry, which was then coated on a copper foil current collector and cut to obtain a negative electrode sheet after drying;

[0124] (3) Assembly of the full battery

[0125] After stacking the positive electrode sheet obtained in step (1), the PP separator, and the negative electrode sheet obtained in step (2), an electrolyte (1 mol / L LiPF6 EC:DMC=3:7 5% FEC) was injected to assemble a button cell. A constant current charge and discharge test was then performed.

[0126] Comparative Example 1:

[0127] The preparation method of the positive and negative electrode sheets and the preparation method of the lithium ion battery provided in this comparative example are the same as those in Example 10. The difference is that the positive electrode sheet used does not contain Li6CoO4, and its composition is LFP:Super-P:PVDF=8:1:1.

[0128] Comparative Example 2:

[0129] The preparation method of the positive and negative electrode sheets and the preparation method of the lithium ion battery provided in this comparative example are the same as those in Example 11. The difference is that the positive electrode sheet used does not contain Li6CoO4, and its composition is LCO:Super-P:PVDF=8:1:1.

[0130] Comparative Example 3:

[0131] The preparation method of the positive and negative electrode sheets and the preparation method of the lithium ion battery provided in this comparative example are the same as those in Example 12. The difference is that the positive electrode sheet used does not contain Li6CoO4, and its composition is NCM811:Super-P:PVDF=8:1:1.

[0132] Figure 4 and Figure 5 The charge and discharge curves and battery cycle performance diagrams of Example 12 and Comparative Example 1 are given. Table 2 shows the first discharge specific capacity and long cycle capacity retention rate of Examples 12-14 and Comparative Examples 1-3, which shows that the Li6CoO4 prepared by the present invention can effectively compensate for the lithium loss in the first cycle of the battery, that is, the cycle process, and prolong the battery life.

[0133] Table 2

[0134]

[0135] In general, the recycling and conversion process provided by the present invention can quickly convert waste LCO positive electrode into reverse fluorite Li6CoO4, and the recycled Li6CoO4 product has higher economic value, which can provide an irreversible capacity of more than 700mAh / g at a lower decomposition potential, thereby fully compensating for the irreversible lithium loss during the SEI formation process. Compared with the most commercially promising positive electrode lithium replenishers (such as Li5FeO4 and Li2NiO2), the obtained Li6CoO4 has better rate performance and higher lithium replenishment capacity, which can effectively improve the capacity and cycle life of the battery.

[0136] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for recycling waste lithium cobalt oxide positive electrode materials into high-performance lithium supplement agents, characterized in that: The following steps are involved: (1) Pretreatment of used LCO batteries: The retired LCO batteries are discharged and then disassembled under inert atmosphere to obtain LCO positive electrode sheets, which are cleaned, dried, and heat treated to collect the failed LCO positive electrode powder that falls off the positive aluminum foil current collector; (2) Synthesis of Li6CoO4 by heat treatment: The collected failed LCO positive electrode powder, lithium source and carbon source are mixed evenly, pressed into tablets, and then rapidly sintered to obtain Li6CoO4 material with an inverse fluorite structure, which is the high-performance lithium supplement.

2. The method for recycling waste lithium cobalt oxide positive electrode materials into high-performance lithium supplement agents according to claim 1, characterized in that: In step (1), the discharge treatment process is specifically as follows: firstly, the waste LCO battery is discharged to 2V, and then it is immersed in a 0.8-1.2 mol / L NaCl aqueous solution to discharge it completely, and the immersion time is 2-12 hours.

3. The method for recycling waste lithium cobalt oxide positive electrode materials into high-performance lithium supplement agents according to claim 1, characterized in that: In step (1), the heat treatment temperature is 400-500° C., the time is 2-3 hours, and the atmosphere is air or oxygen.

4. The method for recycling waste lithium cobalt oxide positive electrode materials into high-performance lithium supplement agents according to claim 1, characterized in that: In step (2), the amount of the spent LCO positive electrode powder and the lithium source added satisfies: the molar ratio of Li to Co is 6:1; The amount of carbon source added satisfies that the spent LCO positive electrode powder and the lithium source can fully react to generate Li6CoO4 and CO2.

5. The method for recycling waste lithium cobalt oxide positive electrode materials into high-performance lithium supplement agents according to claim 1, characterized in that: In step (2), the lithium source is one or more of Li2O, LiOH and Li2CO3; The carbon source is one or more of carbon black, graphite, glucose or starch.

6. The method for recycling waste lithium cobalt oxide positive electrode materials into high-performance lithium supplement agents according to claim 1, characterized in that: In step (2), the mixing method is mortar grinding or mechanical ball milling, the ball milling rate is 200-600r / min, and the ball milling time is 2-8h.

7. The method for recycling waste lithium cobalt oxide positive electrode materials into high-performance lithium supplement agents according to claim 1, characterized in that: In step (2), the rapid sintering treatment adopts Joule heat rapid sintering, the temperature is 800-1200° C., the heating time is 5-20 seconds, and the atmosphere is vacuum or inert atmosphere.

8. A high-performance lithium supplement, prepared by the method according to any one of claims 1 to 7.

9. The use of the high-performance lithium supplement agent according to claim 8, characterized in that: The high-performance lithium supplement agent is added to the positive electrode slurry during the positive electrode homogenization process to supplement the positive electrode with lithium.

10. The use of the high-performance lithium supplement according to claim 9, characterized in that: The solid content of the positive electrode slurry is 30-35%; The positive electrode slurry is prepared from a positive electrode active material, a conductive agent, a binder, a lithium supplement agent and a solvent, and has a solid content of 30-35%. The mass ratio of the positive electrode active material, the conductive agent, the binder and the lithium supplement agent is (76-95): (2-10): (3-10): (2-5); The positive electrode active material is one or more of lithium iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium manganese iron phosphate; The conductive agent is selected from one or more of Super-P, Ketjen black, mesoporous carbon, carbon nanotubes and graphene; The binder is selected from one or more of polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber and polyethyl methacrylate; The solvent is selected from one or more of N-methylpyrrolidone and dimethylformamide.

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