Method for promoting hydrolysis of lithium hexafluorophosphate

Abstract

The invention belongs to the technical field of electrolyte recovery, and particularly relates to a method for promoting hydrolysis of lithium hexafluorophosphate. The hydrolytic agent for promoting hydrolysis of lithium hexafluorophosphate in the electrolyte of the waste lithium ion battery comprises a surfactant, lithium hydroxide and water, and the surfactant comprises an anionic surfactant. According to the method, the mixture obtained after reduced pressure distillation of the waste lithium ion battery electrolyte is mixed with the hydrolytic agent, heating is conducted to enable lithium hexafluorophosphate in the mixture to be fully hydrolyzed, then the hydrolysate is filtered, filter residues are collected, and the lithium element in the waste lithium ion battery electrolyte can be recycled; the method has the advantages of simplicity in operation, low treatment cost, low treatment energy consumption and the like, and has relatively high economic benefits.

Description

Technical Field

[0001] The present application belongs to the technical field of electrolyte recovery, and more specifically, relates to a method for promoting the hydrolysis of lithium hexafluorophosphate. Background Art

[0002] Lithium hexafluorophosphate (LiPF6) is a common coordination compound, mainly used as an electrolyte in lithium-ion batteries and supercapacitors. The literature (Nano Letters, 2024, 24, 2, 533-540) explored the hydrolysis mechanism of LiPF6 in lithium-ion battery electrolyte through theoretical and experimental research. The experiment found that PF6 in pure water - It is well solvated by water. This solvation makes the charge distribution around the ions more uniform, greatly improving the PF6 - The hydrolysis stability makes the hydrolysis reaction difficult to proceed and no hydrolysis occurs; in completely pure (completely anhydrous) organic solvents, PF6 - Hydrolysis is also slow. However, in the electrolyte, due to the dissociation of the counter ions, PF6 - It exists in the electrolyte in a "floating" form, with reduced hydrolysis stability and prone to hydrolysis reaction. However, the inhibitory effect of the hydrolysis product and the reversibility of the hydrolysis reaction make PF6 - Cannot be completely hydrolyzed. Summary of the invention

[0003] In view of the defects of the prior art, the purpose of the present application is to provide a method for promoting the hydrolysis of lithium hexafluorophosphate, aiming to solve the problem that lithium hexafluorophosphate in the electrolyte of waste lithium-ion batteries cannot be completely hydrolyzed.

[0004] To achieve the above objectives, in a first aspect, the present application provides a hydrolyzing agent for promoting the hydrolysis of lithium hexafluorophosphate in waste lithium-ion batteries, which comprises a surfactant, lithium hydroxide and water; The above-mentioned surfactants include anionic surfactants.

[0005] Preferably, the anionic surfactant is selected from one or more of sodium dodecyl sulfate, sodium hexadecyl sulfate, and sodium lauryl alcohol polyoxyethylene ether sulfate.

[0006] Preferably, the above surfactant also includes a nonionic surfactant.

[0007] Preferably, the nonionic surfactant is selected from one or more of NP10 and OP-10.

[0008] Preferably, the mass ratio of the anionic surfactant to the nonionic surfactant is greater than or equal to 7:3.

[0009] Preferably, the amount of the surfactant is 0.3 wt% to 3 wt% of the water.

[0010] Preferably, the mass ratio of the water to the lithium hexafluorophosphate in the waste lithium-ion batteries is (1-10):1.

[0011] Preferably, the molar ratio of the lithium hydroxide to the lithium hexafluorophosphate in the waste lithium-ion battery is greater than or equal to 2:1, and more preferably (2-20):1.

[0012] In a second aspect, the present application provides a method for promoting the hydrolysis of lithium hexafluorophosphate in the electrolyte of waste lithium ion batteries using the above-mentioned hydrolyzing agent, comprising the following steps: The waste lithium-ion battery is disassembled under a protective atmosphere, the electrolyte is taken out, and the solvent in the electrolyte is removed to obtain a mixture containing lithium hexafluorophosphate; then the mixture is mixed with the hydrolyzing agent, and heated to allow the lithium hexafluorophosphate in the mixture to undergo a hydrolysis reaction to obtain a hydrolyzed solution.

[0013] Preferably, the protective atmosphere gas is selected from one or more of nitrogen, argon and helium.

[0014] Preferably, the heating temperature is 20°C to 80°C, and the heating time is 10 to 60 minutes.

[0015] In a third aspect, the present application provides a method for recovering lithium from waste lithium-ion battery electrolyte using the above-mentioned hydrolyzing agent, comprising the following steps: S1. Dismantling the waste battery under a protective atmosphere, taking out the electrolyte, and removing the solvent in the electrolyte to obtain a mixture containing lithium hexafluorophosphate; S2, mixing the above mixture with the above hydrolyzing agent, and heating to allow the lithium hexafluorophosphate in the mixture to undergo a hydrolysis reaction to obtain a hydrolyzed solution; S3, filtering the hydrolyzate, collecting the filter residue, and obtaining a lithium-containing precipitate, thereby recovering the lithium element in the electrolyte of the waste lithium-ion battery.

[0016] Preferably, the protective atmosphere gas is selected from one or more of nitrogen, argon and helium.

[0017] Preferably, the heating temperature is 20°C to 80°C, and the heating time is 10 to 60 minutes.

[0018] In general, the above technical solutions conceived by this application have the following technical advantages compared with the prior art: (1) The hydrolyzing agent provided in the present application for promoting the hydrolysis of lithium hexafluorophosphate in the electrolyte of waste lithium-ion batteries comprises a surfactant, lithium hydroxide and water, wherein the surfactant comprises an anionic surfactant. The mixture of waste lithium-ion battery electrolyte obtained after vacuum distillation and the hydrolyzing agent provided in the present application are mixed and heated so that the lithium hexafluorophosphate in the mixture undergoes a sufficient hydrolysis reaction, reacts with water to generate PF5 precipitate on the one hand, and reacts with lithium hydroxide to generate LiF precipitate and Li3PO4 precipitate on the other hand, thereby effectively recovering the lithium element in the electrolyte of waste lithium-ion batteries.

[0019] (2) The hydrolysis agent provided in the present application for promoting the hydrolysis of lithium hexafluorophosphate in the electrolyte of waste lithium-ion batteries can further weaken the inhibitory effect of the hydrolysis products, the ion solvation effect, etc. through the synergistic effect of anionic surfactants and non-ionic surfactants, thereby further improving the hydrolysis rate of lithium hexafluorophosphate and even achieving complete hydrolysis of lithium hexafluorophosphate in the electrolyte of waste lithium-ion batteries.

[0020] (3) The method provided in the present application for promoting the hydrolysis of lithium hexafluorophosphate in the electrolyte of waste lithium-ion batteries by using the above-mentioned hydrolyzing agent and the method for recovering lithium in the electrolyte of waste lithium-ion batteries have the advantages of simple operation, low processing cost, low processing energy consumption, etc., and have high economic benefits. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present application more clear, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

[0022] In the description of this application, it should be understood that the term "and / or" is a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The symbol " / " herein indicates that the associated objects are in an or relationship, for example, A / B means A or B.

[0023] In the description of the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0024] In the description of the embodiments of the present application, unless otherwise specified, “plurality” means two or more than two.

[0025] Lithium hexafluorophosphate does not hydrolyze in pure water, but it does hydrolyze in trace amounts of water. However, due to the inhibition of hydrolysis products, ion solvation, etc., the hydrolysis of lithium hexafluorophosphate is incomplete, and the lithium element in waste batteries cannot be fully recovered. Based on this, the present application provides a hydrolyzing agent for promoting the hydrolysis of lithium hexafluorophosphate in the electrolyte of waste lithium-ion batteries, which includes a surfactant, lithium hydroxide and water; The above-mentioned surfactants include anionic surfactants.

[0026] The inventor of the present application unexpectedly discovered in an experiment that the waste lithium-ion battery electrolyte is subjected to reduced pressure distillation to remove the solvent to obtain a mixture containing lithium hexafluorophosphate, and then the mixture is mixed with the above-mentioned hydrolyzing agent, and the lithium hexafluorophosphate in the mixture can be fully hydrolyzed by heating, so that the lithium element in the waste lithium-ion battery electrolyte can be effectively recovered. This may be because the surfactant in the hydrolyzing agent can weaken the inhibitory effect of the hydrolysis product, the reversibility of the hydrolysis reaction, etc., so that the lithium hexafluorophosphate in the mixture can be fully hydrolyzed, reacting with water on the one hand to generate PF5 precipitation, and reacting with lithium hydroxide on the other hand to generate LiF precipitation and Li3PO4 precipitation, thereby achieving effective recovery of lithium elements in the waste lithium-ion battery electrolyte.

[0027] In some embodiments, the anionic surfactant is selected from one or more of sodium dodecyl sulfate, sodium hexadecyl sulfate, and sodium lauryl alcohol polyoxyethylene ether sulfate.

[0028] In some embodiments, the surfactant further includes a nonionic surfactant.

[0029] In some embodiments, the mass ratio of the anionic surfactant to the nonionic surfactant is greater than or equal to 7:3.

[0030] In some embodiments, the nonionic surfactant is selected from one or more of NP10 and OP-10.

[0031] In some embodiments, the amount of the surfactant is 0.3 wt % to 3 wt % of the water.

[0032] In some embodiments, the mass ratio of the water to the lithium hexafluorophosphate is (1-10):1.

[0033] In some embodiments, the molar ratio of the lithium hydroxide to the lithium hexafluorophosphate is greater than or equal to 2:1, preferably (2-20):1.

[0034] On the other hand, the present application also provides a method for promoting the hydrolysis of lithium hexafluorophosphate in the electrolyte of waste lithium ion batteries by using the above-mentioned hydrolyzing agent, comprising the following steps: The waste battery is disassembled under a protective atmosphere, the electrolyte is taken out, and the solvent in the electrolyte is removed to obtain a mixture containing lithium hexafluorophosphate; then the mixture is mixed with the hydrolyzing agent, and heated to allow the lithium hexafluorophosphate in the mixture to undergo a hydrolysis reaction to obtain a hydrolyzed solution.

[0035] The mixture containing lithium hexafluorophosphate is mixed with the above-mentioned hydrolyzing agent. On the one hand, the lithium hexafluorophosphate in the mixture reacts with water to generate hydrogen fluoride, phosphorus pentafluoride precipitate and water. The equation is as follows: LiPF6+H2O→HF+PF5↓+LiOH.

[0036] On the other hand, lithium hexafluorophosphate in the mixture reacts with lithium hydroxide according to the following equation: 2LiOH+LiPF6→Li3PO4↓+2LiF↓+H2O.

[0037] The combined effect allows the lithium hexafluorophosphate in the mixture to fully undergo a hydrolysis reaction. The hydrolyzate is filtered and the filter residue is collected, so that the elements in the electrolyte of the waste lithium-ion battery can be fully recovered, among which the lithium element is recovered in the form of PF5 precipitation, LiF precipitation, and Li3PO4 precipitation.

[0038] In some embodiments, the protective atmosphere gas is selected from one or more of nitrogen, argon, and helium.

[0039] It is to be understood that the present application does not limit the above-mentioned method of removing the solvent from the electrolyte, which may be but is not limited to reduced pressure distillation and the like.

[0040] In some embodiments, the heating temperature is 20° C. to 80° C., and the heating time is 10 to 60 minutes.

[0041] In some embodiments, the mixing method may be, but is not limited to, mechanical stirring, ultrasonic mixing, etc.

[0042] On the other hand, the present application also provides a method for recovering lithium from waste lithium-ion battery electrolyte using the above hydrolyzing agent, comprising the following steps: S1. Dismantling the waste battery under a protective atmosphere, taking out the electrolyte, and removing the solvent in the electrolyte to obtain a mixture containing lithium hexafluorophosphate; S2, mixing the above mixture with the above hydrolyzing agent, and heating to allow the lithium hexafluorophosphate in the mixture to undergo a hydrolysis reaction to obtain a hydrolyzed solution; S3, filtering the hydrolyzate, collecting the filter residue, and obtaining a lithium-containing precipitate, thereby recovering the lithium element in the electrolyte of the waste lithium-ion battery.

[0043] It should be understood that materials of the same or similar type, model, quality, nature or function as the reagents and instruments used in the following examples can be used to implement the present application. The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples can be obtained from commercial sources unless otherwise specified.

[0044] The following are examples and comparative examples: Example 1 1) Dismantle and crush the waste lithium-ion batteries under a nitrogen atmosphere to obtain an electrolyte, and then distill the electrolyte under reduced pressure to remove the solvent to obtain a mixture containing lithium hexafluorophosphate.

[0045] 2) The mixture containing lithium hexafluorophosphate is mixed with a hydrolyzing agent obtained by uniformly mixing anionic surfactant sodium dodecyl sulfate (SDS), lithium hydroxide and water, wherein the amount of sodium dodecyl sulfate (SDS) added to the hydrolyzing agent is 0.3wt% of water, the mass ratio of water to lithium hexafluorophosphate in the mixture is 1:1, and the molar ratio of lithium hydroxide to lithium hexafluorophosphate in the mixture is 5:1. The mixture is heated at 30°C for 60 minutes to allow the lithium hexafluorophosphate in the mixture to fully undergo a hydrolysis reaction. On the one hand, the lithium hexafluorophosphate reacts with water to generate PF5 precipitate, and on the other hand, the lithium hexafluorophosphate reacts with lithium hydroxide to generate LiF precipitate and Li3PO4 precipitate, thereby obtaining a hydrolyzed solution.

[0046] 3) Filtering the hydrolyzate to obtain a lithium-containing precipitate, thereby achieving effective recovery of lithium from the electrolyte of the waste lithium-ion battery, determining the content of hexafluorophosphate in the filtrate, and calculating the hydrolysis rate of lithium hexafluorophosphate in the electrolyte of the waste lithium-ion battery.

[0047] Among them, the hydrolysis rate of lithium hexafluorophosphate (%) = ((A1-A2) / A1) × 100%, A1 is the content of hexafluorophosphate in the electrolyte of the waste lithium-ion battery, and A2 is the content of hexafluorophosphate in the filtrate.

[0048] Example 2 1) Dismantle and crush the waste lithium-ion batteries under a nitrogen atmosphere to obtain an electrolyte, and then distill the electrolyte under reduced pressure to remove the solvent to obtain a mixture containing lithium hexafluorophosphate.

[0049] 2) The mixture containing lithium hexafluorophosphate is mixed with a hydrolyzing agent obtained by uniformly mixing anionic surfactant sodium dodecyl sulfate (SDS), lithium hydroxide and water, wherein the amount of sodium dodecyl sulfate (SDS) added to the hydrolyzing agent is 1wt% of water, the mass ratio of water to lithium hexafluorophosphate in the mixture is 5:1, and the molar ratio of lithium hydroxide to lithium hexafluorophosphate in the mixture is 10:1, and heated at 50°C for 30 minutes to allow the lithium hexafluorophosphate in the mixture to fully undergo a hydrolysis reaction to obtain a hydrolyzed solution.

[0050] 3) Filtering the hydrolyzate to obtain a lithium-containing precipitate, thereby effectively recovering the lithium element in the electrolyte of the waste lithium-ion battery, and determining the content of hexafluorophosphate in the filtrate, and then calculating the hydrolysis rate of lithium hexafluorophosphate according to the method provided in Example 1.

[0051] Example 3 1) Dismantle and crush the waste lithium-ion batteries under a nitrogen atmosphere to obtain an electrolyte, and then distill the electrolyte under reduced pressure to remove the solvent to obtain a mixture containing lithium hexafluorophosphate.

[0052] 2) The mixture containing lithium hexafluorophosphate is mixed with a hydrolyzing agent obtained by uniformly mixing anionic surfactant sodium dodecyl sulfate (SDS), lithium hydroxide and water, wherein the amount of sodium dodecyl sulfate (SDS) added to the hydrolyzing agent is 3wt% of water, the mass ratio of water to lithium hexafluorophosphate in the mixture is 10:1, and the molar ratio of lithium hydroxide to lithium hexafluorophosphate in the mixture is 20:1, and heated at 80°C for 10 minutes to allow the lithium hexafluorophosphate in the mixture to fully undergo a hydrolysis reaction to obtain a hydrolyzed solution.

[0053] 3) Filtering the hydrolyzate to obtain a lithium-containing precipitate, thereby effectively recovering the lithium element in the electrolyte of the waste lithium-ion battery, and determining the content of hexafluorophosphate in the filtrate, and then calculating the hydrolysis rate of lithium hexafluorophosphate according to the method provided in Example 1.

[0054] Example 4 1) Dismantle and crush the waste lithium-ion batteries under a nitrogen atmosphere to obtain an electrolyte, and then distill the electrolyte under reduced pressure to remove the solvent to obtain a mixture containing lithium hexafluorophosphate.

[0055] 2) The mixture containing lithium hexafluorophosphate is mixed with a hydrolyzing agent obtained by uniformly mixing anionic surfactant sodium dodecyl sulfate (SDS), lithium hydroxide and water, wherein the amount of sodium dodecyl sulfate (SDS) added to the hydrolyzing agent is 2wt% of water, the mass ratio of water to lithium hexafluorophosphate in the mixture is 10:1, and the molar ratio of lithium hydroxide to lithium hexafluorophosphate in the mixture is 10:1, and heated at 50°C for 30 minutes to allow the lithium hexafluorophosphate in the mixture to fully undergo a hydrolysis reaction to obtain a hydrolyzed solution.

[0056] 3) Filtering the hydrolyzate to obtain a lithium-containing precipitate, thereby effectively recovering the lithium element in the electrolyte of the waste lithium-ion battery, and determining the content of hexafluorophosphate in the filtrate, and then calculating the hydrolysis rate of lithium hexafluorophosphate according to the method provided in Example 1.

[0057] Example 5 1) Dismantle and crush the waste lithium-ion batteries under a nitrogen atmosphere to obtain an electrolyte, and then distill the electrolyte under reduced pressure to remove the solvent to obtain a mixture containing lithium hexafluorophosphate.

[0058] 2) The mixture containing lithium hexafluorophosphate is mixed with a hydrolyzing agent obtained by uniformly mixing anionic surfactant sodium dodecyl sulfate (SDS), nonionic surfactant NP10, lithium hydroxide and water, wherein the amount of surfactant added in the hydrolyzing agent is 1wt% of water (the mass ratio of SDS and NP10 is 7:3), the mass ratio of water to lithium hexafluorophosphate in the mixture is 5:1, and the molar ratio of lithium hydroxide to lithium hexafluorophosphate in the mixture is 10:1, and heated at 30°C for 50 minutes to allow the lithium hexafluorophosphate in the mixture to fully undergo a hydrolysis reaction to obtain a hydrolyzed solution.

[0059] 3) Filtering the hydrolyzate to obtain a lithium-containing precipitate, thereby effectively recovering the lithium element in the electrolyte of the waste lithium-ion battery, and determining the content of hexafluorophosphate in the filtrate, and then calculating the hydrolysis rate of lithium hexafluorophosphate according to the method provided in Example 1.

[0060] Example 6 1) Dismantle and crush the waste lithium-ion batteries under a nitrogen atmosphere to obtain an electrolyte, and then distill the electrolyte under reduced pressure to remove the solvent to obtain a mixture containing lithium hexafluorophosphate.

[0061] 2) The mixture containing lithium hexafluorophosphate is mixed with a hydrolyzing agent obtained by uniformly mixing anionic surfactant sodium dodecyl sulfate (SDS), nonionic surfactant NP10, lithium hydroxide and water, wherein the amount of surfactant added in the hydrolyzing agent is 1wt% of water (the mass ratio of SDS and NP10 is 8:2), the mass ratio of water to lithium hexafluorophosphate in the mixture is 5:1, and the molar ratio of lithium hydroxide to lithium hexafluorophosphate in the mixture is 15:1, and heated at 50°C for 30 minutes to allow the lithium hexafluorophosphate in the mixture to fully undergo a hydrolysis reaction to obtain a hydrolyzed solution.

[0062] 3) Filtering the hydrolyzate to obtain a lithium-containing precipitate, thereby effectively recovering the lithium element in the electrolyte of the waste lithium-ion battery, and determining the content of hexafluorophosphate in the filtrate, and then calculating the hydrolysis rate of lithium hexafluorophosphate according to the method provided in Example 1.

[0063] Example 7 1) Dismantle and crush the waste lithium-ion batteries under a nitrogen atmosphere to obtain an electrolyte, and then distill the electrolyte under reduced pressure to remove the solvent to obtain a mixture containing lithium hexafluorophosphate.

[0064] 2) The mixture containing lithium hexafluorophosphate is mixed with a hydrolyzing agent obtained by uniformly mixing anionic surfactant sodium dodecyl sulfate (SDS), nonionic surfactant NP10, lithium hydroxide and water, wherein the amount of surfactant added in the hydrolyzing agent is 1wt% of water (the mass ratio of SDS and NP10 is 9:1), the mass ratio of water to lithium hexafluorophosphate in the mixture is 5:1, and the molar ratio of lithium hydroxide to lithium hexafluorophosphate in the mixture is 15:1, and heated at 50°C for 30 minutes to allow the lithium hexafluorophosphate in the mixture to fully undergo a hydrolysis reaction to obtain a hydrolyzed solution.

[0065] 3) Filtering the hydrolyzate to obtain a lithium-containing precipitate, thereby effectively recovering the lithium element in the electrolyte of the waste lithium-ion battery, and determining the content of hexafluorophosphate in the filtrate, and then calculating the hydrolysis rate of lithium hexafluorophosphate according to the method provided in Example 1.

[0066] Comparative Example 1 1) Dismantle and crush the waste lithium-ion batteries under a nitrogen atmosphere to obtain an electrolyte, and then distill the electrolyte under reduced pressure to remove the solvent to obtain a mixture containing lithium hexafluorophosphate.

[0067] 2) Mixing the above mixture containing lithium hexafluorophosphate with water, wherein the mass ratio of water to lithium hexafluorophosphate in the mixture is 5:1, and heating at 50° C. for 30 minutes to hydrolyze the lithium hexafluorophosphate in the mixture to obtain a hydrolyzed solution.

[0068] 3) Filter the hydrolyzate to obtain a lithium-containing precipitate, determine the content of hexafluorophosphate in the filtrate, and then calculate the hydrolysis rate of lithium hexafluorophosphate according to the method provided in Example 1.

[0069] Comparative Example 2 1) Dismantle and crush the waste lithium-ion batteries under a nitrogen atmosphere to obtain an electrolyte, and then distill the electrolyte under reduced pressure to remove the solvent to obtain a mixture containing lithium hexafluorophosphate.

[0070] 2) The mixture containing lithium hexafluorophosphate is mixed with a hydrolyzing agent obtained by uniformly mixing lithium hydroxide and water, wherein the mass ratio of water to lithium hexafluorophosphate in the mixture is 5:1, and the molar ratio of lithium hydroxide to lithium hexafluorophosphate in the mixture is 10:1, and heated at 50° C. for 30 min to hydrolyze the lithium hexafluorophosphate in the mixture to obtain a hydrolyzed solution.

[0071] 3) Filter the hydrolyzate to obtain a lithium-containing precipitate, determine the content of hexafluorophosphate in the filtrate, and then calculate the hydrolysis rate of lithium hexafluorophosphate according to the method provided in Example 1.

[0072] Comparative Example 3 1) Dismantle and crush the waste lithium-ion batteries under a nitrogen atmosphere to obtain an electrolyte, and then distill the electrolyte under reduced pressure to remove the solvent to obtain a mixture containing lithium hexafluorophosphate.

[0073] 2) The mixture containing lithium hexafluorophosphate is mixed with a hydrolyzing agent obtained by uniformly mixing a cationic surfactant hexadecyltrimethylammonium chloride (1631), lithium hydroxide and water, wherein the amount of sodium dodecyl sulfate (SDS) added to the hydrolyzing agent is 0.3wt% of water, the mass ratio of water to lithium hexafluorophosphate in the mixture is 5:1, and the molar ratio of lithium hydroxide to lithium hexafluorophosphate in the mixture is 10:1, and heated at 50°C for 30 minutes to allow the lithium hexafluorophosphate in the mixture to undergo a hydrolysis reaction to obtain a hydrolyzed solution.

[0074] 3) Filter the hydrolyzate to obtain a lithium-containing precipitate, determine the content of hexafluorophosphate in the filtrate, and then calculate the hydrolysis rate of lithium hexafluorophosphate according to the method provided in Example 1.

[0075] Comparative Example 4 1) Dismantle and crush the waste lithium-ion batteries under a nitrogen atmosphere to obtain an electrolyte, and then distill the electrolyte under reduced pressure to remove the solvent to obtain a mixture containing lithium hexafluorophosphate.

[0076] 2) The mixture containing lithium hexafluorophosphate is mixed with a hydrolyzing agent obtained by uniformly mixing a nonionic surfactant NP10, lithium hydroxide and water, wherein the amount of the nonionic surfactant added in the hydrolyzing agent is 0.3wt% of water, the mass ratio of water to lithium hexafluorophosphate in the mixture is 5:1, and the molar ratio of lithium hydroxide to lithium hexafluorophosphate in the mixture is 10:1, and heated at 50°C for 30min to hydrolyze the lithium hexafluorophosphate in the mixture to obtain a hydrolyzed solution.

[0077] 3) Filter the hydrolyzate to obtain a lithium-containing precipitate, determine the content of hexafluorophosphate in the filtrate, and then calculate the hydrolysis rate of lithium hexafluorophosphate according to the method provided in Example 1.

[0078] Comparative Example 5 1) Dismantle and crush the waste lithium-ion batteries under a nitrogen atmosphere to obtain an electrolyte, and then distill the electrolyte under reduced pressure to remove the solvent to obtain a mixture containing lithium hexafluorophosphate.

[0079] 2) The mixture containing lithium hexafluorophosphate is mixed with a hydrolyzing agent obtained by uniformly mixing anionic surfactant sodium dodecyl sulfate (SDS), lithium hydroxide and water, wherein the amount of sodium dodecyl sulfate (SDS) added to the hydrolyzing agent is 0.1wt% of water, the mass ratio of water to lithium hexafluorophosphate in the mixture is 5:1, and the molar ratio of lithium hydroxide to lithium hexafluorophosphate in the mixture is 10:1, and heated at 50°C for 30 minutes to hydrolyze the lithium hexafluorophosphate in the mixture to obtain a hydrolyzed solution.

[0080] 3) Filter the hydrolyzate to obtain a lithium-containing precipitate, determine the content of hexafluorophosphate in the filtrate, and then calculate the hydrolysis rate of lithium hexafluorophosphate according to the method provided in Example 1.

[0081] Comparative Example 6 1) Dismantle and crush the waste lithium-ion batteries under a nitrogen atmosphere to obtain an electrolyte, and then distill the electrolyte under reduced pressure to remove the solvent to obtain a mixture containing lithium hexafluorophosphate.

[0082] 2) The mixture containing lithium hexafluorophosphate is mixed with a hydrolyzing agent obtained by uniformly mixing anionic surfactant SDS, nonionic surfactant NP10, lithium hydroxide and water, wherein the amount of surfactant added in the hydrolyzing agent is 0.1wt% of water (the mass ratio of SDS and NP10 is 1:1), the mass ratio of water to lithium hexafluorophosphate in the mixture is 5:1, and the molar ratio of lithium hydroxide to lithium hexafluorophosphate in the mixture is 10:1, and heated at 50°C for 30 minutes to hydrolyze the lithium hexafluorophosphate in the mixture to obtain a hydrolyzed solution.

[0083] 3) Filter the hydrolyzate to obtain a lithium-containing precipitate, determine the content of hexafluorophosphate in the filtrate, and then calculate the hydrolysis rate of lithium hexafluorophosphate according to the method provided in Example 1.

[0084] Table 1 Hydrolysis rate of lithium hexafluorophosphate in Examples 1 to 7 and Comparative Examples 1 to 6

[0085] As can be seen from Table 1, the mixture of waste lithium ion battery electrolyte after vacuum distillation and the hydrolyzing agent provided in the present application are mixed and heated, so that the lithium hexafluorophosphate in the mixture is fully hydrolyzed, and the hydrolysis rate of the lithium hexafluorophosphate is ≥90%. The method for promoting the hydrolysis of lithium hexafluorophosphate in waste lithium ion battery electrolyte and the method for recovering lithium in waste lithium ion battery electrolyte provided in the present application can fully hydrolyze lithium hexafluorophosphate under low cost and low energy consumption conditions, effectively recover lithium in waste lithium ion battery electrolyte, and have high environmental value and economic benefits.

[0086] The hydrolysis rate of lithium hexafluorophosphate in Comparative Example 1 is only 10%. The hydrolysis agent in Comparative Example 2 is prepared by adding lithium hydroxide to the hydrolysis agent in Comparative Example 1, which slightly improves the hydrolysis rate of lithium hexafluorophosphate, but still cannot effectively hydrolyze the lithium hexafluorophosphate.

[0087] The hydrolysis rate of lithium hexafluorophosphate in Comparative Example 3 is only 35%, which indicates that when the surfactant in the hydrolysis agent formula is a cationic surfactant, it cannot promote the hydrolysis of lithium hexafluorophosphate.

[0088] The hydrolysis rates of lithium hexafluorophosphate in Comparative Examples 4 and 6 were 43% and 72%, respectively, which indicates that when the surfactant in the hydrolysis agent formula is only a nonionic surfactant or the content of the nonionic surfactant is too high compared to the anionic surfactant, the hydrolysis of lithium hexafluorophosphate cannot be effectively promoted.

[0089] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A hydrolyzing agent for promoting the hydrolysis of lithium hexafluorophosphate in waste lithium ion batteries, characterized in that: It includes a surfactant, lithium hydroxide and water; The surfactant includes anionic surfactants.

2. The hydrolyzing agent according to claim 1, characterized in that The anionic surfactant is selected from one or more of sodium lauryl sulfate, sodium hexadecyl sulfate, and sodium lauryl alcohol polyoxyethylene ether sulfate.

3. The hydrolyzing agent according to claim 1 or 2, characterized in that The surfactant also includes nonionic surfactants.

4. The hydrolyzing agent according to claim 3, characterized in that The nonionic surfactant is selected from one or more of NP10 and OP-10.

5. The hydrolyzing agent according to claim 4, characterized in that The mass ratio of the anionic surfactant to the nonionic surfactant is greater than or equal to 7:

3.

6. The hydrolyzing agent according to any one of claims 1 to 5, characterized in that The amount of the surfactant is 0.3wt% to 3wt% of the water; and / or, The mass ratio of water to lithium hexafluorophosphate in the waste lithium ion battery is (1-10):1; and / or, The molar ratio of the lithium hydroxide to the lithium hexafluorophosphate in the waste lithium-ion battery is greater than or equal to 2:

1.

7. The hydrolyzing agent according to claim 6, characterized in that The molar ratio of the lithium hydroxide to the lithium hexafluorophosphate is (2-20):

1.

8. A method for promoting the hydrolysis of lithium hexafluorophosphate in the electrolyte of waste lithium ion batteries using the hydrolyzing agent according to any one of claims 1 to 7, characterized in that: The steps include: The waste lithium-ion battery is disassembled under a protective atmosphere, the electrolyte is taken out, and the solvent in the electrolyte is removed to obtain a mixture containing lithium hexafluorophosphate; then the mixture is mixed with the hydrolyzing agent, and heated to allow the lithium hexafluorophosphate in the mixture to undergo a hydrolysis reaction to obtain a hydrolyzed solution.

9. The method according to claim 8, characterized in that The protective atmosphere gas is selected from one or more of nitrogen, argon and helium; and / or, The heating temperature is 20°C to 80°C, and the heating time is 10 to 60 minutes.

10. A method for recovering lithium from waste lithium-ion battery electrolyte using the hydrolyzing agent according to any one of claims 1 to 7, characterized in that: The steps include: S1. Dismantling the waste battery under a protective atmosphere, taking out the electrolyte, and removing the solvent in the electrolyte to obtain a mixture containing lithium hexafluorophosphate; S2, mixing the mixture and the hydrolyzing agent, and heating the mixture to cause the lithium hexafluorophosphate in the mixture to undergo a hydrolysis reaction to obtain a hydrolyzed solution; S3, filtering the hydrolyzate, collecting the filter residue, and obtaining a lithium-containing precipitate, thereby recovering the lithium element in the electrolyte of the waste lithium-ion battery.

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