Salicylic acid-based eutectic solvent, preparation method thereof and method for leaching valuable metal in waste lithium cobalt oxide battery positive electrode material

Abstract

The invention discloses a salicylic acid-based eutectic solvent, a preparation method thereof and a method for leaching valuable metals in a positive electrode material of a waste lithium cobalt oxide battery. The technical method is a salicylic acid-based eutectic solvent consisting of salicylic acid and a hydrogen bond acceptor, and the method for leaching the valuable metals in the waste lithium cobalt oxide battery positive electrode material by using the salicylic acid-based eutectic solvent comprises the following steps: (1) carrying out high-temperature treatment on the waste lithium cobalt oxide battery positive electrode material to obtain a pretreated material; mixing the pretreated material with a salicylic acid-based eutectic solvent, carrying out closed heating at 100-120 DEG C to react for 6-8 hours, and respectively recovering and leaching valuable metals and leachate in the positive electrode material of the waste lithium cobalt oxide battery; the salicylic acid-based eutectic solvent is low in price, wide in source and low in preparation cost, salicylic acid can be recycled, the recovery cost is reduced, the leaching method has the advantages of being good in environment, low in energy consumption, non-toxic, harmless, high in efficiency and the like, and a new thought is provided for the field of battery recovery; the method belongs to the field of battery recovery and eutectic solvents.

Description

Technical Field

[0001] The invention discloses a salicylic acid-based low eutectic solvent, and also discloses a preparation method of the salicylic acid-based low eutectic solvent and a leaching method of valuable metals in anode materials of waste lithium cobalt oxide batteries by using the salicylic acid-based low eutectic solvent. The invention belongs to the field of battery recovery and low eutectic solvents. Background Art

[0002] In recent years, the rapid development of the new energy vehicle industry has led to a substantial increase in the production of lithium-ion batteries, accompanied by a surge in the number of waste lithium-ion batteries. According to estimates, by 2030, the number of waste lithium-ion batteries in the world will reach 11 million tons. Waste lithium cobalt oxide batteries contain a large amount of valuable metal elements such as lithium and cobalt. Among them, cobalt, as a metal widely used in the industrial field, has extremely high economic benefits. As the scale of lithium-ion battery manufacturing increases, the demand for cobalt will also increase significantly. In addition, waste lithium-ion batteries contain toxic compounds such as heavy metal elements, organic and inorganic compounds. If improperly handled, they will pollute the environment. Among them, cobalt is carcinogenic, mutagenic and reproductively toxic, which will cause irreparable damage to the human body. The recycling of waste lithium batteries is of great significance in alleviating the shortage of metal resources and protecting the environment.

[0003] At present, there are two main methods for recycling waste lithium-ion battery positive electrode materials: pyrometallurgical recycling and wet recycling.

[0004] The pyrometallurgical recovery process consumes a lot of energy, produces a lot of waste gas, cannot effectively separate metals, and has low product purity.

[0005] The technology is relatively mature, with high metal recovery rate and high product purity, but the process is long, consumes a lot of acid, produces a lot of acidic wastewater, and causes secondary pollution.

[0006] Therefore, it is necessary to find an efficient green recycling method for waste lithium-ion batteries that can reduce energy consumption and secondary pollution.

[0007] Deep eutectic solvent (DES) is a new type of green solvent, composed of hydrogen bond donors and hydrogen bond acceptors, with good solubility and metal coordination ability, which can leach valuable metals from the cathode materials of waste lithium-ion batteries through reduction and coordination reactions. The preparation of deep eutectic solvents is simple, non-volatile, biodegradable, and recyclable. Using deep eutectic solvents to recycle waste lithium-ion batteries can not only avoid harm to the environment, but also efficiently recycle metals.

[0008] CN 114438343 A bifunctional hydrophobic deep eutectic solvent for selective extraction of lithium and its preparation method and application method, the bifunctional hydrophobic deep eutectic solvent comprises a hydrogen bond donor and a hydrogen bond acceptor; the hydrogen bond donor comprises a β-diketone extractant and / or phenyl salicylate; the hydrogen bond acceptor comprises a phosphorus extractant and / or N,N-dialkylbenzamide, the bifunctional hydrophobic deep eutectic solvent is used for selective extraction and separation of lithium in a high sodium and low lithium solution, but is not suitable for leaching lithium and cobalt elements from waste cobalt oxide lithium positive electrode material black powder. Because the lithium and cobalt in the waste cobalt oxide lithium battery positive electrode material exist in the form of cobalt oxide and cobalt tetraoxide respectively, it is necessary to first reduce the cobalt to a divalent cobalt form, and then destroy the structure of the lithium cobalt oxide through the acidity provided by the low eutectic solvent, so that the lithium and cobalt can be released from the waste cobalt oxide lithium battery positive electrode material black powder structure into the solution. The above reaction process requires that the low eutectic solvent has reducing ability and acidity. The reducing ability and acidity of the above-mentioned bifunctional hydrophobic low eutectic solvent are weak, and it is impossible to release lithium and cobalt elements from the black powder structure of waste lithium cobalt oxide positive electrode materials into the solution; while the salicylic acid-based low eutectic solvent has stronger reducing ability and acidity, so the salicylic acid-based low eutectic solvent is more suitable for leaching lithium and cobalt elements from the black powder of waste lithium cobalt oxide positive electrode materials. Summary of the invention

[0009] In view of the above problems, the first object of the present invention is to provide a salicylic acid-based low eutectic solvent for leaching valuable metals in the positive electrode material of waste lithium cobalt oxide batteries.

[0010] The second object of the present invention is a method for preparing the salicylic acid-based deep eutectic solvent.

[0011] The third purpose of the present invention is the salicylic acid-based low eutectic solvent and the method for leaching valuable metals in the positive electrode material of waste lithium cobalt oxide batteries. The salicylic acid-based low eutectic solvent is used to leach the valuable metals in the positive electrode material of waste lithium cobalt oxide batteries. The conditions are green and mild, no additional reducing agent needs to be added, the leaching efficiency is high, the salicylic acid used can be recycled and reused, and it has good application prospects.

[0012] The first technical solution provided by the present invention is as follows:

[0013] A salicylic acid-based low eutectic solvent is prepared from salicylic acid and a hydrogen bond acceptor; the molar ratio of the salicylic acid to the hydrogen bond acceptor is 1:(1-3).

[0014] In the present invention, the molar ratio of salicylic acid to hydrogen bond acceptor is specifically 1:1, 1:2, 1:3. The present invention has no special limitation on the source of the above raw materials, and conventional commercial products can be used.

[0015] Furthermore, in the above-mentioned salicylic acid-based low eutectic solvent, the hydrogen bond acceptor includes at least one of choline chloride, glycine, and anhydrous betaine.

[0016] The salicylic acid-based low eutectic solvent is used to leach valuable metals from the positive electrode materials of waste lithium cobalt oxide batteries.

[0017] Another technical solution provided by the present invention is a method for preparing the above-mentioned salicylic acid-based low eutectic solvent, which comprises mixing salicylic acid and a hydrogen bond acceptor, and reacting the mixture at 60 to 80° C. for 20 to 30 minutes to obtain a salicylic acid-based low eutectic solvent.

[0018] More preferably: the reaction temperature is 80°C and the reaction time is 20 min.

[0019] In the present invention, the reaction is carried out under stirring, and the stirring speed is 600 rpm.

[0020] Another technical solution provided by the present invention is a method for leaching valuable metals in the positive electrode material of waste lithium cobalt oxide batteries, comprising the following steps:

[0021] (1) calcining the waste lithium cobalt oxide battery positive electrode material at 300-500° C. for 3-5 hours to obtain a pretreated material;

[0022] (2) The pretreated material obtained in step (1) is mixed with the salicylic acid-based low eutectic solvent described in the first technical solution, and the mixture is heated in a closed manner at 100 to 120° C. for 6 to 8 hours to recover the valuable metals and leachate in the leached waste lithium cobalt oxide battery positive electrode material.

[0023] More preferably, the calcination temperature is 500° C. and the calcination time is 3 hours. In the present invention, the purpose of the high temperature treatment is to remove impurities such as electrolyte and binder remaining in the cathode material of waste lithium cobalt oxide batteries.

[0024] Furthermore, the above-mentioned method for leaching valuable metals in waste lithium cobalt oxide battery positive electrode materials also includes a method for recovering salicylic acid from the leachate obtained by the leaching reaction, comprising the following steps: diluting the leachate with deionized water, precipitating salicylic acid crystals after standing for a period of time; filtering and separating, and obtaining salicylic acid crystals after drying.

[0025] Preferably, the dilution ratio of deionized water in step (1) is 10 to 20 times.

[0026] Furthermore, in the above-mentioned method for leaching valuable metals in waste lithium cobalt oxide battery positive electrode materials, the mass ratio of the pretreated material in step (2) to the salicylic acid-based low eutectic solvent is 1:(30-50); more preferably 1:50.

[0027] In the present invention, the conditions of the closed heating reaction preferably include: temperature of 120° C. and time of 8 h. In the present invention, the closed heating reaction is preferably carried out under stirring, and the stirring speed is preferably 600 rpm.

[0028] Furthermore, in the above-mentioned method for leaching valuable metals from the positive electrode material of waste lithium cobalt oxide batteries, the valuable metals include one or both of lithium and cobalt.

[0029] Preferably, the valuable metal includes one or both of lithium and cobalt.

[0030] The leaching rate (η) of valuable metals in the cathode material of waste lithium cobalt oxide batteries is defined by the following formula:

[0031] η=(CV / C0V0)×100%;

[0032] Where C is the final concentration of valuable metals in the leachate (mg L -1 ), detected by atomic absorption spectroscopy; V represents the volume of the leaching solution (L); C0 is the concentration of valuable metals in the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material (mg L -1 ), detected by atomic absorption spectroscopy, V0 is the volume (L) of the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material.

[0033] Compared with the prior art, the technical solution provided by the present invention has the following technical advantages:

[0034] 1. The raw materials of the salicylic acid-based deep eutectic solvent of the present invention are low in price, widely available, easy to prepare, and salicylic acid can be recycled and reused, thereby reducing the recycling cost.

[0035] 2. The leaching method of valuable metals in the positive electrode material of waste lithium cobalt oxide batteries provided by the present invention can replace the traditional wet recovery process using strong acid, does not need to add additional reducing agents, has good leaching effect, short leaching time, and has high efficiency in recovering valuable metals lithium and cobalt in the positive electrode material of waste lithium cobalt oxide batteries. The leaching rate of valuable metal element lithium is: 90.36% to 100%, and the leaching rate of cobalt is: 88.14% to 96.84%.

[0036] 3. After the leaching reaction is completed, the salicylic acid-based low eutectic solvent provided by the present invention can be diluted by adding deionized water to precipitate salicylic acid in the form of crystals, and lithium and cobalt can remain in the leachate in the form of ions. The salicylic acid and the leachate are filtered and separated to achieve the recycling of salicylic acid. After washing and drying, salicylic acid can still be used to prepare a new salicylic acid-based low eutectic solvent, and the prepared salicylic acid-based low eutectic solvent also has good leaching ability.

[0037] Among them, the recovery rate of salicylic acid is 63.76% to 85.38%. The salicylic acid-based low eutectic solvent prepared using the recovered salicylic acid still has good leaching performance. The leaching rate of valuable metal lithium is 89.86% to 97.51%, and the leaching rate of cobalt is 85.71% to 94.38%. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below in conjunction with specific examples, but does not constitute any limitation to the present invention.

[0039] Example 1

[0040] The salicylic acid-based deep eutectic solvent of this embodiment is a mixture of a hydrogen bond acceptor and a hydrogen bond donor, wherein the hydrogen bond acceptor is choline chloride, the hydrogen bond donor is salicylic acid, and the molar ratio of choline chloride to salicylic acid is 1:3.

[0041] The preparation method is as follows: choline chloride and salicylic acid are mixed in a molar ratio of 1:3, and heated at a temperature of 80° C. and a stirring speed of 600 rpm for 30 minutes to obtain a low eutectic solvent.

[0042] The method for leaching valuable metals in the positive electrode material of waste lithium cobalt oxide batteries provided in this embodiment comprises the following steps:

[0043] (1) placing the waste lithium cobalt oxide battery positive electrode material in a muffle furnace at 300° C. for 5 hours to remove the binder and residual electrolyte, cooling to room temperature and then grinding to separate the aluminum foil, and sieving to obtain the lithium cobalt oxide battery positive electrode material powder;

[0044] (2) 1 g of the lithium cobalt oxide battery positive electrode material powder obtained in step (1) and 30 g of the low eutectic solvent prepared in this example were added into a 20 ml glass bottle, placed in an oil bath and heated at 100 ° C. and 600 rpm for 8 h, and filtered to obtain a leachate containing valuable metals lithium and cobalt;

[0045] (3) The original waste lithium cobalt oxide battery positive electrode material described in step (1) is digested with aqua regia and digested in a forced air oven at 160° C. for 5 h. The metal element content of the digested solution and the leaching solution is detected by atomic absorption spectroscopy, and the leaching rates of lithium ions and cobalt ions are calculated respectively.

[0046] The leaching rate (η) of valuable metals in the cathode material of waste lithium cobalt oxide batteries is defined by the following formula:

[0047] η=(CV / C0V0)×100%;

[0048] Where C is the final concentration of valuable metals in the leachate (mg L -1), detected by atomic absorption spectroscopy; V represents the volume of the leaching solution (L); C0 is the concentration of valuable metals in the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material (mg L -1 ), detected by atomic absorption spectroscopy, V0 is the volume (L) of the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material.

[0049] After testing and calculation, the leaching rates of valuable metal elements lithium and cobalt were 93.84% and 89.08% respectively.

[0050] Example 2

[0051] The salicylic acid-based deep eutectic solvent of this embodiment is a mixture of a hydrogen bond acceptor and a hydrogen bond donor, wherein the hydrogen bond acceptor is glycine, the hydrogen bond donor is salicylic acid, and the molar ratio of glycine to salicylic acid is 1:3.

[0052] The preparation method is as follows: glycine and salicylic acid are mixed in a molar ratio of 1:3, and heated at a temperature of 90° C. and a stirring speed of 600 rpm for 25 minutes to obtain a low eutectic solvent.

[0053] The method for leaching valuable metals in the positive electrode material of waste lithium cobalt oxide batteries provided in this embodiment comprises the following steps:

[0054] (1) placing the waste lithium cobalt oxide battery positive electrode material in a muffle furnace at 400° C. for 4 hours to remove the binder and residual electrolyte, cooling to room temperature and then grinding to separate the aluminum foil, and sieving to obtain the lithium cobalt oxide battery positive electrode material powder;

[0055] (2) 1 g of the lithium cobalt oxide battery positive electrode material powder obtained in step (1) and 40 g of the low eutectic solvent prepared in this example were added to a 20 ml glass bottle, placed in an oil bath and heated at 110° C. and 600 rpm for 7 h, and filtered to obtain a leachate containing valuable metals lithium and cobalt;

[0056] (3) The original waste lithium cobalt oxide battery positive electrode material described in step (1) is digested with aqua regia and digested in a forced air oven at 160° C. for 5 h. The metal element content of the digested solution and the leaching solution is detected by atomic absorption spectroscopy, and the leaching rates of lithium ions and cobalt ions are calculated respectively.

[0057] The leaching rate (η) of valuable metals in the cathode material of waste lithium cobalt oxide batteries is defined by the following formula:

[0058] η=(CV / C0V0)×100%;

[0059] Where C is the final concentration of valuable metals in the leachate (mg L -1), detected by atomic absorption spectroscopy; V represents the volume of the leaching solution (L); C0 is the concentration of valuable metals in the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material (mg L -1 ), detected by atomic absorption spectroscopy, V0 is the volume (L) of the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material.

[0060] After testing and calculation, the leaching rates of valuable metal elements lithium and cobalt were 94.96% and 91.54% respectively.

[0061] Example 3

[0062] The salicylic acid-based deep eutectic solvent of this embodiment is a mixture of a hydrogen bond acceptor and a hydrogen bond donor, wherein the hydrogen bond acceptor is anhydrous betaine, the hydrogen bond donor is salicylic acid, and the molar ratio of anhydrous betaine to salicylic acid is 1:3.

[0063] The preparation method comprises the following steps: mixing anhydrous betaine and salicylic acid in a molar ratio of 1:3, and heating at a temperature of 100° C. and a stirring speed of 600 rpm for 20 minutes to obtain a low eutectic solvent.

[0064] The method for leaching valuable metals in the positive electrode material of waste lithium cobalt oxide batteries provided in this embodiment comprises the following steps:

[0065] (1) placing the waste lithium cobalt oxide battery positive electrode material in a muffle furnace at 500° C. for 3 hours to remove the binder and residual electrolyte, cooling to room temperature and then grinding to separate the aluminum foil, and sieving to obtain the lithium cobalt oxide battery positive electrode material powder;

[0066] (2) 1 g of the lithium cobalt oxide battery positive electrode material powder obtained in step (1) and 50 g of the low eutectic solvent prepared in this example were added to a 20 ml glass bottle, placed in an oil bath and heated at 120° C. and 600 rpm for 6 h, and filtered to obtain a leachate containing valuable metals lithium and cobalt;

[0067] (3) The original waste lithium cobalt oxide battery positive electrode material described in step (1) is digested with aqua regia and digested in a forced air oven at 160° C. for 5 h. The metal element content of the digested solution and the leaching solution is detected by atomic absorption spectroscopy, and the leaching rates of lithium ions and cobalt ions are calculated respectively.

[0068] The leaching rate (η) of valuable metals in the cathode material of waste lithium cobalt oxide batteries is defined by the following formula:

[0069] η=(CV / C0V0)×100%;

[0070] Where C is the final concentration of valuable metals in the leachate (mg L -1), detected by atomic absorption spectroscopy; V represents the volume of the leaching solution (L); C0 is the concentration of valuable metals in the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material (mg L -1 ), detected by atomic absorption spectroscopy, V0 is the volume (L) of the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material.

[0071] After testing and calculation, the leaching rates of valuable metal elements lithium and cobalt were 93.73% and 90.14% respectively.

[0072] Example 4

[0073] The salicylic acid-based deep eutectic solvent of this embodiment is a mixture of a hydrogen bond acceptor and a hydrogen bond donor, wherein the hydrogen bond acceptor is choline chloride, the hydrogen bond donor is salicylic acid, and the molar ratio of choline chloride to salicylic acid is 1:2.

[0074] The preparation method is as follows: choline chloride and salicylic acid are mixed in a molar ratio of 1:2, and heated at a temperature of 100° C. and a stirring speed of 600 rpm for 20 minutes to obtain a low eutectic solvent.

[0075] The method for leaching valuable metals in the positive electrode material of waste lithium cobalt oxide batteries provided in this embodiment comprises the following steps:

[0076] (1) placing the waste lithium cobalt oxide battery positive electrode material in a muffle furnace at 500° C. for 3 hours to remove the binder and residual electrolyte, cooling to room temperature and then grinding to separate the aluminum foil, and sieving to obtain the lithium cobalt oxide battery positive electrode material powder;

[0077] (2) 1 g of the lithium cobalt oxide battery positive electrode material powder obtained in step (1) and 40 g of the low eutectic solvent prepared in this example were added to a 20 ml glass bottle, placed in an oil bath and heated at 110° C. and 600 rpm for 7 h, and filtered to obtain a leachate containing valuable metals lithium and cobalt;

[0078] (3) The original waste lithium cobalt oxide battery positive electrode material described in step (1) is digested with aqua regia and digested in a forced air oven at 160° C. for 5 h. The metal element content of the digested solution and the leaching solution is detected by atomic absorption spectroscopy, and the leaching rates of lithium ions and cobalt ions are calculated respectively.

[0079] The leaching rate (η) of valuable metals in the cathode material of waste lithium cobalt oxide batteries is defined by the following formula:

[0080] η=(CV / C0V0)×100%;

[0081] Where C is the final concentration of valuable metals in the leachate (mg L -1), detected by atomic absorption spectroscopy; V represents the volume of the leaching solution (L); C0 is the concentration of valuable metals in the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material (mg L -1 ), detected by atomic absorption spectroscopy, V0 is the volume (L) of the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material.

[0082] After testing and calculation, the leaching rates of valuable metal elements lithium and cobalt were 96.37% and 94.56% respectively.

[0083] Example 5

[0084] The salicylic acid-based deep eutectic solvent of this embodiment is a mixture of a hydrogen bond acceptor and a hydrogen bond donor, wherein the hydrogen bond acceptor is glycine, the hydrogen bond donor is salicylic acid, and the molar ratio of glycine to salicylic acid is 1:2.

[0085] The preparation method comprises the following steps: mixing anhydrous betaine and salicylic acid in a molar ratio of 1:2, and heating at a temperature of 80°C and a stirring speed of 600 rpm for 30 minutes to obtain a low eutectic solvent.

[0086] The method for leaching valuable metals in the positive electrode material of waste lithium cobalt oxide batteries provided in this embodiment comprises the following steps:

[0087] (1) placing the waste lithium cobalt oxide battery positive electrode material in a muffle furnace at 300° C. for 5 hours to remove the binder and residual electrolyte, cooling to room temperature and then grinding to separate the aluminum foil, and sieving to obtain the lithium cobalt oxide battery positive electrode material powder;

[0088] (2) 1 g of the lithium cobalt oxide battery positive electrode material powder obtained in step (1) and 50 g of the low eutectic solvent prepared in this example were added to a 20 ml glass bottle, placed in an oil bath and heated at 120° C. and 600 rpm for 6 h, and filtered to obtain a leachate containing valuable metals lithium and cobalt;

[0089] (3) The original waste lithium cobalt oxide battery positive electrode material described in step (1) is digested with aqua regia and digested in a forced air oven at 160° C. for 5 h. The metal element content of the digested solution and the leaching solution is detected by atomic absorption spectroscopy, and the leaching rates of lithium ions and cobalt ions are calculated respectively.

[0090] The leaching rate (η) of valuable metals in the cathode material of waste lithium cobalt oxide batteries is defined by the following formula:

[0091] η=(CV / C0V0)×100%;

[0092] Where C is the final concentration of valuable metals in the leachate (mg L -1), detected by atomic absorption spectroscopy; V represents the volume of the leaching solution (L); C0 is the concentration of valuable metals in the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material (mg L -1 ), detected by atomic absorption spectroscopy, V0 is the volume (L) of the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material.

[0093] After testing and calculation, the leaching rates of valuable metal elements lithium and cobalt were 97.55% and 92.37% respectively.

[0094] Example 6

[0095] The salicylic acid-based deep eutectic solvent of this embodiment is a mixture of a hydrogen bond acceptor and a hydrogen bond donor, wherein the hydrogen bond acceptor is anhydrous betaine, the hydrogen bond donor is salicylic acid, and the molar ratio of anhydrous betaine to salicylic acid is 1:2.

[0096] The preparation method comprises the following steps: mixing anhydrous betaine and salicylic acid in a molar ratio of 1:2, and heating at a temperature of 90° C. and a stirring speed of 600 rpm for 25 minutes to obtain a low eutectic solvent.

[0097] The method for leaching valuable metals in the positive electrode material of waste lithium cobalt oxide batteries provided in this embodiment comprises the following steps:

[0098] (1) placing the waste lithium cobalt oxide battery positive electrode material in a muffle furnace at 400° C. for 4 hours to remove the binder and residual electrolyte, cooling to room temperature and then grinding to separate the aluminum foil, and sieving to obtain the lithium cobalt oxide battery positive electrode material powder;

[0099] (2) 1 g of the lithium cobalt oxide battery positive electrode material powder obtained in step (1) and 30 g of the low eutectic solvent prepared in this example were added into a 20 ml glass bottle, placed in an oil bath and heated at 100 ° C. and 600 rpm for 8 h, and filtered to obtain a leachate containing valuable metals lithium and cobalt;

[0100] (3) The original waste lithium cobalt oxide battery positive electrode material described in step (1) is digested with aqua regia and digested in a forced air oven at 160° C. for 5 h. The metal element content of the digested solution and the leaching solution is detected by atomic absorption spectroscopy, and the leaching rates of lithium ions and cobalt ions are calculated respectively.

[0101] The leaching rate (η) of valuable metals in the cathode material of waste lithium cobalt oxide batteries is defined by the following formula:

[0102] η=(CV / C0V0)×100%;

[0103] Where C is the final concentration of valuable metals in the leachate (mg L -1), detected by atomic absorption spectroscopy; V represents the volume of the leaching solution (L); C0 is the concentration of valuable metals in the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material (mg L -1 ), detected by atomic absorption spectroscopy, V0 is the volume (L) of the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material.

[0104] After testing and calculation, the leaching rates of valuable metal elements lithium and cobalt were 90.36% and 88.14% respectively.

[0105] Example 7

[0106] The salicylic acid-based deep eutectic solvent of this embodiment is a mixture of a hydrogen bond acceptor and a hydrogen bond donor, wherein the hydrogen bond acceptor is choline chloride, the hydrogen bond donor is salicylic acid, and the molar ratio of choline chloride to salicylic acid is 1:1.

[0107] The preparation method is as follows: choline chloride and salicylic acid are mixed in a molar ratio of 1:1, and heated at a temperature of 90° C. and a stirring speed of 600 rpm for 25 minutes to obtain a low eutectic solvent.

[0108] The method for leaching valuable metals in the positive electrode material of waste lithium cobalt oxide batteries provided in this embodiment comprises the following steps:

[0109] (1) placing the waste lithium cobalt oxide battery positive electrode material in a muffle furnace at 400° C. for 4 hours to remove the binder and residual electrolyte, cooling to room temperature and then grinding to separate the aluminum foil, and sieving to obtain the lithium cobalt oxide battery positive electrode material powder;

[0110] (2) 1 g of the lithium cobalt oxide battery positive electrode material powder obtained in step (1) and 50 g of the low eutectic solvent prepared in this example were added to a 20 ml glass bottle, placed in an oil bath and heated at 120° C. and 600 rpm for 6 h, and filtered to obtain a leachate containing valuable metals lithium and cobalt;

[0111] (3) The original waste lithium cobalt oxide battery positive electrode material described in step (1) is digested with aqua regia and digested in a forced air oven at 160° C. for 5 h. The metal element content of the digested solution and the leaching solution is detected by atomic absorption spectroscopy, and the leaching rates of lithium ions and cobalt ions are calculated respectively.

[0112] The leaching rate (η) of valuable metals in the cathode material of waste lithium cobalt oxide batteries is defined by the following formula:

[0113] η=(CV / C0V0)×100%;

[0114] Where C is the final concentration of valuable metals in the leachate (mg L -1), detected by atomic absorption spectroscopy; V represents the volume of the leaching solution (L); C0 is the concentration of valuable metals in the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material (mg L -1 ), detected by atomic absorption spectroscopy, V0 is the volume (L) of the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material.

[0115] After testing and calculation, the leaching rates of valuable metal elements lithium and cobalt are 100.00% and 96.84% respectively.

[0116] Example 8

[0117] The salicylic acid-based deep eutectic solvent of this embodiment is a mixture of a hydrogen bond acceptor and a hydrogen bond donor, wherein the hydrogen bond acceptor is glycine, the hydrogen bond donor is salicylic acid, and the molar ratio of glycine to salicylic acid is 1:1.

[0118] The preparation method is as follows: glycine and salicylic acid are mixed in a molar ratio of 1:1, and heated at a temperature of 100° C. and a stirring speed of 600 rpm for 20 minutes to obtain a low eutectic solvent.

[0119] The method for leaching valuable metals in the positive electrode material of waste lithium cobalt oxide batteries provided in this embodiment comprises the following steps:

[0120] (1) placing the waste lithium cobalt oxide battery positive electrode material in a muffle furnace at 500° C. for 3 hours to remove the binder and residual electrolyte, cooling to room temperature and then grinding to separate the aluminum foil, and sieving to obtain the lithium cobalt oxide battery positive electrode material powder;

[0121] (2) 1 g of the lithium cobalt oxide battery positive electrode material powder obtained in step (1) and 30 g of the low eutectic solvent prepared in this example were added into a 20 ml glass bottle, placed in an oil bath and heated at 100 ° C. and 600 rpm for 8 h, and filtered to obtain a leachate containing valuable metals lithium and cobalt;

[0122] (3) The original waste lithium cobalt oxide battery positive electrode material described in step (1) is digested with aqua regia and digested in a forced air oven at 160° C. for 5 h. The metal element content of the digested solution and the leaching solution is detected by atomic absorption spectroscopy, and the leaching rates of lithium ions and cobalt ions are calculated respectively.

[0123] The leaching rate (η) of valuable metals in the cathode material of waste lithium cobalt oxide batteries is defined by the following formula:

[0124] η=(CV / C0V0)×100%;

[0125] Where C is the final concentration of valuable metals in the leachate (mg L -1), detected by atomic absorption spectroscopy; V represents the volume of the leaching solution (L); C0 is the concentration of valuable metals in the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material (mg L -1 ), detected by atomic absorption spectroscopy, V0 is the volume (L) of the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material.

[0126] After testing and calculation, the leaching rates of valuable metal elements lithium and cobalt were 92.84% and 90.76% respectively.

[0127] Example 9

[0128] The salicylic acid-based deep eutectic solvent of this embodiment is a mixture of a hydrogen bond acceptor and a hydrogen bond donor, wherein the hydrogen bond acceptor is anhydrous betaine, the hydrogen bond donor is salicylic acid, and the molar ratio of anhydrous betaine to salicylic acid is 1:1.

[0129] The preparation method comprises the following steps: mixing anhydrous betaine and salicylic acid in a molar ratio of 1:1, and heating at a temperature of 80°C and a stirring speed of 600 rpm for 30 minutes to obtain a low eutectic solvent.

[0130] The method for leaching valuable metals in the positive electrode material of waste lithium cobalt oxide batteries provided in this embodiment comprises the following steps:

[0131] (1) placing the waste lithium cobalt oxide battery positive electrode material in a muffle furnace at 300° C. for 5 hours to remove the binder and residual electrolyte, cooling to room temperature and then grinding to separate the aluminum foil, and sieving to obtain the lithium cobalt oxide battery positive electrode material powder;

[0132] (2) 1 g of the lithium cobalt oxide battery positive electrode material powder obtained in step (1) and 40 g of the low eutectic solvent prepared in this example were added to a 20 ml glass bottle, placed in an oil bath and heated at 110° C. and 600 rpm for 7 h, and filtered to obtain a leachate containing valuable metals lithium and cobalt;

[0133] (3) The original waste lithium cobalt oxide battery positive electrode material described in step (1) is digested with aqua regia and digested in a forced air oven at 160° C. for 5 h. The metal element content of the digested solution and the leaching solution is detected by atomic absorption spectroscopy, and the leaching rates of lithium ions and cobalt ions are calculated respectively.

[0134] The leaching rate (η) of valuable metals in the cathode material of waste lithium cobalt oxide batteries is defined by the following formula:

[0135] η=(CV / C0V0)×100%;

[0136] Where C is the final concentration of valuable metals in the leachate (mg L -1), detected by atomic absorption spectroscopy; V represents the volume of the leaching solution (L); C0 is the concentration of valuable metals in the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material (mg L -1 ), detected by atomic absorption spectroscopy, V0 is the volume (L) of the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material.

[0137] After testing and calculation, the leaching rates of valuable metal elements lithium and cobalt were 92.55% and 89.28% respectively.

[0138] Example 10

[0139] The salicylic acid-based deep eutectic solvent of this embodiment is a mixture of a hydrogen bond acceptor and a hydrogen bond donor, wherein the hydrogen bond acceptor is choline chloride, the hydrogen bond donor is recycled salicylic acid, and the molar ratio of choline chloride to recycled salicylic acid is 1:1.

[0140] The preparation method comprises the following steps: mixing choline chloride and recovered salicylic acid in a molar ratio of 1:1, and heating at a temperature of 100° C. and a stirring speed of 600 rpm for 20 minutes to obtain a low eutectic solvent.

[0141] The method for leaching valuable metals in the positive electrode material of waste lithium cobalt oxide batteries provided in this embodiment comprises the following steps:

[0142] (1) placing the waste lithium cobalt oxide battery positive electrode material in a muffle furnace at 500° C. for 3 hours to remove the binder and residual electrolyte, cooling to room temperature and then grinding to separate the aluminum foil, and sieving to obtain the lithium cobalt oxide battery positive electrode material powder;

[0143] (2) 1 g of the lithium cobalt oxide battery positive electrode material powder obtained in step (1) and 40 g of the low eutectic solvent prepared in this example were added to a 20 ml glass bottle, placed in an oil bath and heated at 110° C. and 600 rpm for 7 h, and filtered to obtain a leachate containing valuable metals lithium and cobalt;

[0144] (3) The original waste lithium cobalt oxide battery positive electrode material described in step (1) is digested with aqua regia and digested in a forced air oven at 160° C. for 5 h. The metal element content of the digested solution and the leaching solution is detected by atomic absorption spectroscopy, and the leaching rates of lithium ions and cobalt ions are calculated respectively.

[0145] The leaching rate (η) of valuable metals in the cathode material of waste lithium cobalt oxide batteries is defined by the following formula:

[0146] η=(CV / C0V0)×100%;

[0147] Where C is the final concentration of valuable metals in the leachate (mg L -1), detected by atomic absorption spectroscopy; V represents the volume of the leaching solution (L); C0 is the concentration of valuable metals in the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material (mg L -1 ), detected by atomic absorption spectroscopy, V0 is the volume (L) of the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material.

[0148] After testing and calculation, the leaching rates of valuable metal elements lithium and cobalt were 93.36% and 90.40% respectively.

[0149] Embodiment 11

[0150] The salicylic acid-based deep eutectic solvent of this embodiment is a mixture of a hydrogen bond acceptor and a hydrogen bond donor, wherein the hydrogen bond acceptor is choline chloride, the hydrogen bond donor is recycled salicylic acid, and the molar ratio of choline chloride to recycled salicylic acid is 1:1.

[0151] The preparation method is as follows: choline chloride and recovered salicylic acid are mixed in a molar ratio of 1:1, and heated at a temperature of 90° C. and a stirring speed of 600 rpm for 25 minutes to obtain a low eutectic solvent.

[0152] The method for leaching valuable metals in the positive electrode material of waste lithium cobalt oxide batteries provided in this embodiment comprises the following steps:

[0153] (1) placing the waste lithium cobalt oxide battery positive electrode material in a muffle furnace at 400° C. for 4 hours to remove the binder and residual electrolyte, cooling to room temperature and then grinding to separate the aluminum foil, and sieving to obtain the lithium cobalt oxide battery positive electrode material powder;

[0154] (2) 1 g of the lithium cobalt oxide battery positive electrode material powder obtained in step (1) and 50 g of the low eutectic solvent prepared in this example were added to a 20 ml glass bottle, placed in an oil bath and heated at 120° C. and 600 rpm for 6 h, and filtered to obtain a leachate containing valuable metals lithium and cobalt;

[0155] (3) The original waste lithium cobalt oxide battery positive electrode material described in step (1) is digested with aqua regia and digested in a forced air oven at 160° C. for 5 h. The metal element content of the digested solution and the leaching solution is detected by atomic absorption spectroscopy, and the leaching rates of lithium ions and cobalt ions are calculated respectively.

[0156] The leaching rate (η) of valuable metals in the cathode material of waste lithium cobalt oxide batteries is defined by the following formula:

[0157] η=(CV / C0V0)×100%;

[0158] Where C is the final concentration of valuable metals in the leachate (mg L -1), detected by atomic absorption spectroscopy; V represents the volume of the leaching solution (L); C0 is the concentration of valuable metals in the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material (mg L -1 ), detected by atomic absorption spectroscopy, V0 is the volume (L) of the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material.

[0159] After testing and calculation, the leaching rates of valuable metal elements lithium and cobalt were 97.51% and 94.38% respectively.

[0160] Example 12

[0161] The salicylic acid-based deep eutectic solvent of this embodiment is a mixture of a hydrogen bond acceptor and a hydrogen bond donor, wherein the hydrogen bond acceptor is choline chloride, the hydrogen bond donor is recycled salicylic acid, and the molar ratio of choline chloride to recycled salicylic acid is 1:1.

[0162] The preparation method is as follows: choline chloride and recovered salicylic acid are mixed in a molar ratio of 1:1, and heated at a temperature of 80° C. and a stirring speed of 600 rpm for 30 minutes to obtain a low eutectic solvent.

[0163] The method for leaching valuable metals in the positive electrode material of waste lithium cobalt oxide batteries provided in this embodiment comprises the following steps:

[0164] (1) placing the waste lithium cobalt oxide battery positive electrode material in a muffle furnace at 300° C. for 5 hours to remove the binder and residual electrolyte, cooling to room temperature and then grinding to separate the aluminum foil, and sieving to obtain the lithium cobalt oxide battery positive electrode material powder;

[0165] (2) 1 g of the lithium cobalt oxide battery positive electrode material powder obtained in step (1) and 30 g of the low eutectic solvent prepared in this example were added into a 20 ml glass bottle, placed in an oil bath and heated at 100 ° C. and 600 rpm for 8 h, and filtered to obtain a leachate containing valuable metals lithium and cobalt;

[0166] (3) The original waste lithium cobalt oxide battery positive electrode material described in step (1) is digested with aqua regia and digested in a forced air oven at 160° C. for 5 h. The metal element content of the digested solution and the leaching solution is detected by atomic absorption spectroscopy, and the leaching rates of lithium ions and cobalt ions are calculated respectively.

[0167] The leaching rate (η) of valuable metals in the cathode material of waste lithium cobalt oxide batteries is defined by the following formula:

[0168] η=(CV / C0V0)×100%;

[0169] Where C is the final concentration of valuable metals in the leachate (mg L -1), detected by atomic absorption spectroscopy; V represents the volume of the leaching solution (L); C0 is the concentration of valuable metals in the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material (mg L -1 ), detected by atomic absorption spectroscopy, V0 is the volume (L) of the aqua regia digestion solution of the original waste lithium cobalt oxide battery positive electrode material.

[0170] After testing and calculation, the leaching rates of valuable metal elements lithium and cobalt were 89.86% and 85.71% respectively.

[0171] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be clearly pointed out that professionals in this field can make appropriate modifications and improvements without departing from the principles of the present invention. Any modifications and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A salicylic acid-based deep eutectic solvent, characterized in that: The salicylic acid-based low eutectic solvent is prepared from salicylic acid and a hydrogen bond acceptor; the molar ratio of salicylic acid to the hydrogen bond acceptor is 1:(1-3).

2. The salicylic acid-based deep eutectic solvent according to claim 1, characterized in that The hydrogen bond acceptor includes at least one of choline chloride, glycine, and anhydrous betaine.

3. The salicylic acid-based deep eutectic solvent according to claim 1 is used to leach valuable metals from waste lithium cobalt oxide battery positive electrode materials.

4. The method for preparing the salicylic acid-based deep eutectic solvent according to claim 1, characterized in that: The method comprises mixing salicylic acid and a hydrogen bond acceptor, reacting the mixture at 60 to 80° C. for 20 to 30 minutes to obtain a salicylic acid-based low eutectic solvent.

5. A method for leaching valuable metals from waste lithium cobalt oxide battery positive electrode materials, characterized in that: The following steps are involved: (1) calcining the waste lithium cobalt oxide battery positive electrode material at 300-500° C. for 3-5 hours to obtain a pretreated material; (2) The pretreated material obtained in step (1) is mixed with the salicylic acid-based low eutectic solvent described in claim 1, and the mixture is heated in a closed manner at 100 to 120° C. for 6 to 8 hours, and the valuable metals and the leachate in the leached waste lithium cobalt oxide battery positive electrode material are respectively recovered.

6. The method for leaching valuable metals from the positive electrode material of waste lithium cobalt oxide batteries according to claim 5, characterized in that: The mass ratio of the pretreated material in step (2) to the salicylic acid-based low eutectic solvent is 1:(30-50).

7. The method for leaching valuable metals from the positive electrode material of waste lithium cobalt oxide batteries according to claim 5, characterized in that: The valuable metal includes one or both of lithium and cobalt.

8. The method for leaching valuable metals from the positive electrode material of waste lithium cobalt oxide batteries according to claim 5, characterized in that: The method also includes step (3) of recovering salicylic acid from the leaching solution obtained by the leaching reaction.

9. The method for leaching valuable metals from the positive electrode material of waste lithium cobalt oxide batteries according to claim 8, characterized in that: The method for recovering salicylic acid from the leachate obtained by the leaching reaction comprises the following steps: The leaching solution is diluted with deionized water, and salicylic acid crystals are precipitated after standing; the salicylic acid crystals are obtained after filtration, separation, and drying.

10. The method for leaching valuable metals from the positive electrode material of waste lithium cobalt oxide batteries according to claim 8, characterized in that: The dilution ratio of deionized water in step (1) is 10 to 20 times.