A method for improving stability of a chemical prelithiation solution

Abstract

The embodiment of the present application relates to a method for improving the stability of a chemical prelithiation solution and a novel chemical prelithiation solution, the method comprising: configuring a chemical prelithiation solution with an ether solvent and an aromatic compound and metal lithium, and adding an additive containing anion X to form a novel chemical prelithiation solution at the same time or after the configuration of the chemical prelithiation solution is completed, wherein the anion in the additive containing anion X is anion X having a coordination ability with lithium ions, and the anion X participates in the coordination structure in the chemical prelithiation solution to stabilize the lithium ions in the chemical prelithiation solution and slow down the disproportionation reaction of the effective component Li1A in the chemical prelithiation solution to form the coordination structure of the aromatic anion and more than one lithium ion Li y A during storage. The generation of Li1A is a complex formed by the aromatic anion A and lithium ions.

Description

Technical Field

[0001] This invention relates to the field of lithium battery electrode chemical pre-lithiation technology, and in particular to a method for improving the stability of chemical pre-lithiation solutions. Background Technology

[0002] Lithium-ion batteries are widely used in electric vehicles, portable electronic devices, and power tools due to their high energy density and long lifespan. However, the formation of a solid electrolyte layer at the positive and negative electrode interface consumes some of the active lithium resources within the battery, resulting in irreversible loss of active lithium and reducing battery energy density. Researchers have proposed compensating for this loss of active lithium within the battery through pre-lithiation technology.

[0003] Pre-lithiation technology is a technique that introduces active lithium into electrode materials through physical, chemical, or electrochemical methods. Currently proposed pre-lithiation methods include additive lithium replenishment, contact pre-lithiation, chemical pre-lithiation, and electrochemical pre-lithiation. Among these, chemical pre-lithiation involves immersing the electrode material in an organic lithium solution containing active lithium ions (i.e., a pre-lithiation solution), causing lithium ions to intercalate into the electrode material. The intercalated active lithium is released during battery cycling to compensate for the loss of active lithium within the battery. Compared to other lithium replenishment techniques, chemical pre-lithiation technology has advantages such as simple operation, high lithium replenishment efficiency, and ease of large-scale production.

[0004] However, the organic lithium solutions currently in use have poor chemical stability. We have found that after standing at room temperature for a period of time, the organic lithium solutions slowly fail, resulting in a decrease in the pre-lithiation effect or even complete failure. This invention explores and studies the problem of poor stability of chemical pre-lithiation solutions. Summary of the Invention

[0005] The purpose of this invention is to provide a method for improving the stability of a chemical pre-lithiation solution and a novel chemical pre-lithiation solution. By introducing an anion X, which has coordination ability with lithium ions, into the chemical pre-lithiation solution to participate in the coordination structure, the lithium ions in the chemical pre-lithiation solution are stabilized. This slows down the disproportionation reaction of the effective component Li1A during storage, which forms a coordination structure Li1A between an aromatic hydrocarbon anion and more than one lithium ion. y The generation of A, where 1 < y ≤ 6, improves the stability of the chemical pre-lithiation solution.

[0006] Therefore, in a first aspect, embodiments of the present invention provide a method for improving the stability of a chemically pre-lithiated solution, the method comprising:

[0007] A chemical pre-lithiation solution is prepared with ether solvents and aromatic hydrocarbon compounds and metallic lithium. Simultaneously or after the preparation of the chemical pre-lithiation solution, an additive containing anion X is added to form a novel chemical pre-lithiation solution. The anion in the additive containing anion X is anion X that has coordination ability with lithium ions. This allows the anion X in the additive to participate in the coordination structure in the chemical pre-lithiation solution, thereby stabilizing the lithium ions in the chemical pre-lithiation solution and mitigating the disproportionation reaction of its effective component Li1A during storage, which forms a coordination structure of aromatic hydrocarbon anions with more than one lithium ion. y The generation of A; wherein, 1 < y ≤ 6, and the Li1A is a complex formed by the aromatic hydrocarbon anion A and lithium ions.

[0008] Preferably, the additive containing anion X is a soluble metal salt or an alkali metal salt.

[0009] More preferably, the soluble lithium salt includes one or more combinations of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium perchlorate (LiClO4), lithium nitrate (LiNO3), lithium difluorooxalate borate (LiODFB), lithium dioxalate borate (LiBOB), and lithium borohydride (LiBH4).

[0010] More preferably, the additive containing anion X is a soluble sodium salt, including NaPF6.

[0011] Preferably, in the novel chemical pre-lithiation solution, the concentration of the additive containing anion X is 0.001 mol / L to 10 mol / L.

[0012] Preferably, the backbone of the ether solvent is composed of carbon atoms and oxygen atoms, and contains no or one or more substituents.

[0013] More preferably, the ether solvent includes one or more of the following: ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, and tetrahydropyran.

[0014] Preferably, the aromatic hydrocarbon compound contains one or more benzene rings, and the benzene rings may or may not contain substituents.

[0015] Preferably, the aromatic hydrocarbon compound includes one or more of naphthalene and its derivatives, biphenyl and its derivatives, and phenanthrene and its derivatives.

[0016] Secondly, embodiments of the present invention provide a novel chemical pre-lithiation solution, obtained by any of the methods described in the first aspect for improving the stability of the chemical pre-lithiation solution.

[0017] The method for improving the stability of a chemically pre-lithiated solution provided in this invention introduces an anion X, which has coordination ability with lithium ions, into the chemically pre-lithiated solution to participate in the coordination structure of the solution. This stabilizes the lithium ions in the solution and slows down the disproportionation reaction of the effective component Li1A during storage, which forms a coordination structure Li1A between an aromatic hydrocarbon anion and more than one lithium ion. y The generation of A improves the stability of the chemical pre-lithiation solution. Attached Figure Description

[0018] Figure 1 This is a schematic diagram illustrating the failure principle of a chemically pre-lithiated solution.

[0019] Figure 2 This is a schematic diagram illustrating the principle of improving the stability of chemical pre-lithiation solutions and suppressing their failure, as described in an embodiment of the present invention.

[0020] Figure 3 The first-week electrochemical curve of the original nano-silicon electrode used in Example 1;

[0021] Figure 4 The constant current charge-discharge test curves of the nano-silicon anode after the chemical pre-lithiation solution was left to stand for different times in Example 1 are shown.

[0022] Figure 5 The constant current charge-discharge test curves of the nano-silicon anode after being pre-lithiated by the chemical pre-lithiation solution in Comparative Example 1 after being left to stand for different times are shown.

[0023] Figure 6 The first-week electrochemical curves of the original graphite electrodes used in Example 2 and Comparative Example 2;

[0024] Figure 7 The constant current charge-discharge test curves of the nano-silicon anode after the chemical pre-lithiation solution was left to stand for different times in Example 2 are shown.

[0025] Figure 8 The constant current charge-discharge test curves of the nano-silicon anode after being pre-lithiated by the chemical pre-lithiation solution in Comparative Example 2 after being left to stand for different times are shown. Detailed Implementation

[0026] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0027] This invention provides a method for improving the stability of a chemically prelithiated solution and a novel chemically prelithiated solution.

[0028] In the application of silicon-based anode materials, the initial efficiency is very low because a large number of lithium ions are consumed during the first charge and discharge process to form a solid electrolyte film on its surface, which severely restricts its application in batteries. Pre-lithiation is an effective method to improve the initial efficiency of silicon-based anode materials. Among them, the aromatic hydrocarbon chemical pre-lithiation method avoids the problems of dendrites and by-products that occur with direct lithium metal pre-lithiation, and also allows for quantitative control of the pre-lithiation process, thus gaining widespread application.

[0029] However, in practical applications, the applicant found that the currently widely used organic lithium solutions have poor chemical stability. After standing at room temperature for a period of time, the organic lithium solutions slowly fail, resulting in a decrease in the pre-lithiation effect or even complete failure. We have conducted research, experiments and analysis on the causes of failure.

[0030] Research, experiments, and analysis results indicate that the failure of widely used chemical pre-lithiation solution systems using ether solvents and aromatic hydrocarbon lithium salts is primarily due to the thermodynamic instability of the anions released from the aromatic hydrocarbon lithium salts in the solvent. The anions of aromatic hydrocarbon compounds tend to combine with multiple lithium ions to form thermodynamically more stable coordination compounds, such as... Figure 1 As shown, this type of ligand does not have pre-lithiation capability, so as the solution stands for a longer time, it will cause the chemical pre-lithiation solution to slowly fail.

[0031] In response, the applicant, through research and experimentation, proposed a method to improve the stability of chemically pre-lithiated solutions. This method involves introducing anions with strong lithium-ion binding affinity into the chemically pre-lithiated solution to participate in the coordination structure. By "fixing" lithium ions with these additive anions, the binding force between aromatic hydrocarbon anions and lithium ions is reduced, forming a more stable and effective lithium-replenishing component, thereby mitigating the failure of the pre-lithiated solution to a certain extent. The principle is as follows: Figure 2 As shown.

[0032] The method for improving the stability of a chemical pre-lithiation solution proposed in this invention specifically includes: preparing a chemical pre-lithiation solution with lithium metal using an ether solvent and an aromatic hydrocarbon compound; and adding an additive containing anion X simultaneously with or after the preparation of the chemical pre-lithiation solution to form a novel chemical pre-lithiation solution. The anion in the additive containing anion X is anion X that has coordination ability with lithium ions, allowing the anion X in the additive to participate in the coordination structure in the chemical pre-lithiation solution, thereby stabilizing the lithium ions in the chemical pre-lithiation solution and slowing down the disproportionation reaction of its effective component Li1A during storage, forming a coordination structure Li1A between an aromatic hydrocarbon anion and more than one lithium ion. y The generation of A is 1 < y ≤ 6.

[0033] Li1A is a complex formed by aromatic hydrocarbon anion A and lithium ion;

[0034] Preferably, the coordination ability mentioned above specifically means that the coordination ability of anion X with lithium ion is stronger than or approximately the coordination ability of aromatic hydrocarbon anion A with lithium ion in aromatic hydrocarbon compounds.

[0035] In this invention, the additive containing anion X is a soluble metal salt or an alkali metal salt, preferably a soluble lithium salt, and more preferably includes one or more combinations of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium perchlorate (LiClO4), lithium nitrate (LiNO3), lithium difluorooxalate borate (LiODFB), lithium dioxalate borate (LiBOB), and lithium borohydride (LiBH4).

[0036] The introduction of lithium salts is mainly due to the fact that the combination of anions and lithium ions leads to a decrease in the concentration of lithium ions. Therefore, the addition of metallic lithium salts is used to introduce anions while maintaining the concentration of lithium ions that can participate in the chemical pre-lithiation process.

[0037] Of course, using other soluble salts, such as soluble sodium salts, specifically NaPF6, as additives containing anion X can also slow down the failure of pre-lithium solutions.

[0038] In the novel chemical pre-lithiation solution of the present invention, the concentration of the additive containing anion X is 0.001 mol / L-10 mol / L.

[0039] Ether solvents have a backbone composed of carbon and oxygen atoms, and may or may not contain one or more substituents. Preferably, ether solvents include one or more of the following: ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, and tetrahydropyran. Aromatic hydrocarbon compounds contain one or more benzene rings, which may or may not contain substituents. Preferably, they include one or more of naphthalene and its derivatives, biphenyl and its derivatives, and phenanthrene and its derivatives.

[0040] The novel chemical pre-lithiation solution obtained by the above methods has the advantages of good stability and long storage time. By using additives to slow down the failure of the chemical pre-lithiation solution, in addition to improving its stability, production costs can be reduced. Frequent preparation of fresh chemical pre-lithiation solution is unnecessary during production, thus increasing the utilization rate of the solution and reducing the proportion of failed and discarded solutions. This also reduces pollutant emissions and effectively lowers the pollution caused by ether reagents and aromatic hydrocarbons.

[0041] To better understand the technical solution provided by this invention, the following examples illustrate the method and application of this invention for improving the stability of chemically pre-lithiated solutions.

[0042] Example 1

[0043] Step a), take 50 mL of 2-methyltetrahydrofuran (2-Me-THF) solvent;

[0044] Step b): Add 7.70 g of biphenyl (Bp) to the 2-methyltetrahydrofuran solvent in a), stir magnetically for 30 mins, and obtain a homogeneous and clear solution;

[0045] Step c) Add 0.35 g of lithium metal foil to the homogeneous and clear solution obtained in b) and stir magnetically for 120 mins to obtain a homogeneous, dark-colored 1 mol / L chemical pre-lithiation solution.

[0046] Step d): Add 7.60 g of lithium hexafluorophosphate to the chemical prelithiation solution obtained in c), and stir magnetically for 30 mins to obtain a chemical prelithiation solution Li-Bp / 2-Me-THF containing 1 mol / L LiPF6 additive.

[0047] Two portions of the solution were prepared according to the above method. After preparation, the solutions were allowed to stand for 3 hours and 24 hours, respectively, and then used for pre-lithiation of the nano-silicon electrode.

[0048] The chemical pre-lithiation solution obtained in step c) above was used as Comparative Example 1. Two portions were prepared and allowed to stand for 3 hours and 24 hours, respectively, before being used for pre-lithiation of the nano-silicon anode.

[0049] The pre-lithiation process is as follows: the nano-silicon electrode is immersed in the chemical pre-lithiation solution prepared above for 5 minutes, followed by rinsing the electrode twice with 2-methyltetrahydrofuran, and then drying at 60 degrees Celsius for 2 hours. This yields experimental electrode 1 (pre-lithiated after 3 hours of standing), experimental electrode 2 (pre-lithiated after 24 hours of standing), and control electrode 1 (pre-lithiated after 3 hours of standing), and control electrode 2 (pre-lithiated after 24 hours of standing).

[0050] The original nano-silicon electrode, experimental electrode 1, experimental electrode 2, control electrode 1, and control electrode 2 were assembled with lithium sheets to form half-cells. The half-cells were subjected to constant current charge-discharge tests at a current density of 100 mA / g and a voltage range of 0.005V-1.5V.

[0051] Figure 3 The first-week electrochemical curve of the original nano-silicon electrode used in Example 1; Figure 4 The constant current charge-discharge test curves of the nano-silicon anode after the chemical pre-lithiation solution was left to stand for different times in Example 1 are shown. Figure 5 The constant current charge-discharge test curves of the nano-silicon anode after being pre-lithiated by the chemical pre-lithiation solution in Comparative Example 1 after being left to stand for different times are shown.

[0052] Electrochemical tests showed that the first-cycle cycle efficiency of the silicon nanosheet treated with a pre-lithiation solution containing additives for 3 hours increased from 92% to 124%. The silicon nanosheet treated with a pre-lithiation solution containing additives for 24 hours still exhibited a high first-cycle coulombic efficiency of 117%, indicating that the performance of the pre-lithiation solution only slightly declined. The first-cycle cycle efficiency of the silicon nanosheet treated with a pre-lithiation solution without additives for 3 hours was 122%, while the first-cycle cycle efficiency of the silicon nanosheet treated with a pre-lithiation solution without additives for 24 hours was only 101%, showing a significant decline compared to the 3-hour treatment.

[0053] Example 2

[0054] Step a), take 50 mL of 2-methyltetrahydrofuran (2-Me-THF) solvent;

[0055] Step b): Add 6.41 g of naphthalene to the 2-methyltetrahydrofuran solvent in a), stir magnetically for 30 mins, and obtain a homogeneous and clear solution;

[0056] Step c): Add 2.87 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to the homogeneous solution in b), stir magnetically for 30 min, and obtain a homogeneous and clear solution;

[0057] In step d), 0.35 g of lithium metal foil was added to the homogeneous solution obtained in c), and the mixture was magnetically stirred for 120 min to obtain a homogeneous, dark-colored 1 mol / L chemical pre-lithiation solution Li-Naph / 2-Me-THF containing 0.2 mol / L LiTFSI additive.

[0058] Two portions of the solution were prepared according to the above method. After preparation, the solutions were allowed to stand for 3 hours and 24 hours, respectively, and then used for pre-lithiation of the graphite electrode.

[0059] The chemical pre-lithiation solution obtained by LiTFSI in step c) above was used as Comparative Example 2, with the remaining steps being the same but without the addition of the above steps. Two portions were prepared in the same way, and after being left to stand, they were used to pre-lithiate the graphite electrode after standing for 3 hours and 24 hours, respectively.

[0060] The pre-lithiation process is as follows: the graphite electrode sheet is immersed in the chemical pre-lithiation solution prepared above for 10 minutes, followed by rinsing the electrode sheet twice with 2-methyltetrahydrofuran, and then drying at 60 degrees Celsius for 2 hours. This yields experimental electrode sheet 3 (pre-lithiated after 3 hours of standing), experimental electrode sheet 4 (pre-lithiated after 24 hours of standing), and control electrode sheet 3 (pre-lithiated after 3 hours of standing), and control electrode sheet 4 (pre-lithiated after 24 hours of standing).

[0061] Graphite electrode sheets, experimental electrode 3, experimental electrode 4, control electrode 3, and control electrode 4 were assembled with lithium sheets to form half-cells. The half-cells were subjected to constant current charge-discharge tests at a current density of 100 mA / g and a voltage range of 0V-3V.

[0062] Figure 6 The first-week electrochemical curve of the original graphite electrode sheet used in Example 2; Figure 7 The constant current charge-discharge test curves of the nano-silicon anode after the chemical pre-lithiation solution was left to stand for different times in Example 2 are shown. Figure 8 The constant current charge-discharge test curves of the nano-silicon anode after being pre-lithiated by the chemical pre-lithiation solution in Comparative Example 2 after being left to stand for different times are shown.

[0063] Electrochemical tests showed that after pre-lithiation of the graphite electrode with a pre-lithiation solution containing additives prepared for 3 hours, the first-cycle cycle efficiency of the graphite electrode increased from 85% to 138%. After treatment with a pre-lithiation solution containing additives prepared for 24 hours, the first-cycle coulombic efficiency of the graphite electrode was 126%, indicating a slight degradation in the performance of the pre-lithiation solution. The first-cycle coulombic efficiency of the graphite electrode treated with a pre-lithiation solution without additives prepared for 3 hours was 129%, while the efficiency after treatment with a pre-lithiation solution without additives prepared for 24 hours was only 102%, showing a significant degradation.

[0064] Example 3

[0065] Step a), take 50 mL of tetrahydrofuran solvent;

[0066] Step b): Add 3.85 g of biphenyl to the tetrahydrofuran solvent in a), stir magnetically for 30 min, and obtain a homogeneous and clear solution;

[0067] Step c) Add 1.52 g of lithium hexafluorophosphate to the solution obtained in b) and stir magnetically for 30 min until a homogeneous and clear solution is obtained;

[0068] In step d), 0.175 g of lithium metal foil was added to the homogeneous solution obtained in c), and the mixture was magnetically stirred for 120 min to obtain a homogeneous, dark-colored 0.5 mol / L chemically pre-lithiated solution Li-Naph / THF containing 0.2 mol / L LiPF6 additive.

[0069] Two portions of the solution were prepared according to the above method. After preparation, the solutions were allowed to stand for 3 hours and 24 hours, respectively, and then used for pre-lithiation of the nano-silicon electrode.

[0070] The chemical pre-lithiation solution obtained by following the same steps but without adding the LiPF6 additive in step c) above was used as Comparative Example 3. Two portions were prepared in the same way. After preparation, the portions were allowed to stand for 3 hours and 24 hours, respectively, and then used for pre-lithiation of nano-silicon electrodes.

[0071] The pre-lithiation process is as follows: the nano-silicon electrode is immersed in the chemical pre-lithiation solution prepared above for 5 minutes, followed by rinsing the electrode twice with 2-methyltetrahydrofuran, and then drying at 60 degrees Celsius for 2 hours. This yields experimental electrode 5 (pre-lithiated after 3 hours of standing), experimental electrode 6 (pre-lithiated after 24 hours of standing), and control electrode 5 (pre-lithiated after 3 hours of standing), and control electrode 6 (pre-lithiated after 24 hours of standing).

[0072] Nano-silicon electrodes, experimental electrode 5, experimental electrode 6, control electrode 5, and control electrode 6 were assembled with lithium sheets to form half-cells. The half-cells were subjected to constant current charge-discharge tests at a current density of 100 mA / g and a voltage range of 0.005V-1.5V.

[0073] Due to the influence of the pre-lithiation solution potential, the solution itself is not as efficient for nano-silicon as in Example 1. The first-cycle cycle efficiency of the nano-silicon electrode treated with the solution prepared for 3 hours is 106%, and the first-cycle cycle efficiency of the nano-silicon electrode treated with the solution prepared for 24 hours is 103%. The pre-lithiation solution without additives obtained first-cycle coulombic efficiencies of 104% and 95% after 3 hours and 24 hours, respectively, indicating that the additives still maintain a relatively good stabilizing effect.

[0074] Example 4

[0075] Step a), take 50 mL of ethylene glycol dimethyl ether solvent;

[0076] Step b): Add 6.41 g of biphenyl to the 2-methyltetrahydrofuran solvent in a), stir magnetically for 30 min, and obtain a homogeneous and clear solution;

[0077] Step c) Add 0.35 g of lithium metal foil to the homogeneous solution obtained in b) and stir magnetically for 120 min to obtain a homogeneous, dark-colored 1 mol / L chemical pre-lithiation solution.

[0078] In step d), 1.87 g of lithium difluorosulfonylimide was added to the chemical pre-lithiation solution obtained in c), and the mixture was magnetically stirred for 30 min to obtain a chemical pre-lithiation solution Li-Naph / DME containing 0.2 mol / L LiFSI additive.

[0079] Two portions of the solution were prepared according to the above method. After preparation, the solutions were allowed to stand for 3 hours and 24 hours, respectively, and then used for pre-lithiation of the tin anode sheet.

[0080] The chemical pre-lithiation solution obtained in step c) above was used as Comparative Example 4. Two portions were prepared and allowed to stand for 3 hours and 24 hours, respectively, before being used for pre-lithiation of the tin anode sheet.

[0081] The pre-lithiation process is as follows: The tin negative electrode is immersed in the prepared chemical pre-lithiation solution for 5 minutes, followed by rinsing the electrode twice with ethylene glycol dimethyl ether solvent, and then drying at 60 degrees Celsius for 2 hours. This yields experimental electrode 7 (pre-lithiated after 3 hours of standing), experimental electrode 8 (pre-lithiated after 24 hours of standing), and control electrode 7 (pre-lithiated after 3 hours of standing), and control electrode 8 (pre-lithiated after 24 hours of standing).

[0082] Tin negative electrode, experimental electrode 7, experimental electrode 8, control electrode 7, and control electrode 8 were assembled with lithium foil to form half-cells. The half-cells were subjected to constant current charge-discharge tests at a current density of 100 mA / g and a voltage range of 0.01V-2V.

[0083] After treatment with a pre-lithiation solution containing additives for 3 hours, the first-cycle efficiency of the tin anode increased from 76% to 86%. After treatment with the pre-lithiation solution containing additives for 24 hours, the first-cycle efficiency of the tin anode was 83%. The first-cycle efficiency of the tin anode treated with the pre-lithiation solution without additives for 3 hours was 86%, and the first-cycle efficiency of the tin anode treated with the pre-lithiation solution containing additives for 24 hours was 81%. This shows that the pre-lithiation performance of the pre-lithiation solution containing additives is well maintained.

[0084] Example 5

[0085] Step a), take 50 mL of 2-methyltetrahydrofuran solvent:

[0086] Step b): Add 8.41 4-methylbiphenyl (4 MBp) to the 2-methyltetrahydrofuran solvent in a), stir magnetically for 30 min, and obtain a homogeneous and clear solution;

[0087] Step c) Add 0.35 g of lithium metal foil to the homogeneous solution obtained in b) and stir magnetically for 120 min to obtain a homogeneous, dark-colored 1 mol / L chemical pre-lithiation solution.

[0088] Step d): Add 7.20 g of lithium difluorooxalate borate (LiODFB) to the chemical prelithiation solution obtained in c), and stir magnetically for 30 min to obtain a chemical prelithiation solution Li-4MBp / 2-Me-THF containing 1 mol / L LiODFB additive.

[0089] Two portions of the solution were prepared according to the above method. After preparation, the solutions were allowed to stand for 3 hours and 24 hours, respectively, and then used for pre-lithiation of the silicon-oxygen / carbon composite anode.

[0090] The chemical pre-lithiation solution obtained in step c) above was used as Comparative Example 5. Two portions were prepared and allowed to stand for 3 hours and 24 hours, respectively, before being used for pre-lithiation of the silicon-oxygen / carbon composite anode.

[0091] The pre-lithiation process is as follows: the silicon-oxygen / carbon composite negative electrode is immersed in the chemical pre-lithiation solution prepared above for 5 minutes, followed by rinsing the electrode twice with 2-methyltetrahydrofuran solvent, and then drying at 60 degrees Celsius for 2 hours. This yields experimental electrode 9 (pre-lithiated after 3 hours of standing), experimental electrode 10 (pre-lithiated after 24 hours of standing), and control electrode 9 (pre-lithiated after 3 hours of standing) and control electrode 10 (pre-lithiated after 24 hours of standing).

[0092] The silicon-oxygen / carbon composite negative electrode, experimental electrode 9, experimental electrode 10, control electrode 9, and control electrode 10 were assembled with lithium sheets to form half-cells. The half-cells were subjected to constant current charge-discharge tests at a current density of 100 mA / g and a voltage range of 0.005V-1.5V.

[0093] After treatment with a pre-lithiation solution containing additives for 3 hours, the first-cycle efficiency of the silicon-oxygen / carbon composite anode increased from 71% to 110%. After treatment with the pre-lithiation solution containing additives for 24 hours, the first-cycle efficiency of the silicon-oxygen / carbon composite anode was 103%. The first-cycle efficiency of the silicon-oxygen / carbon composite anode treated with the pre-lithiation solution without additives for 3 hours was 104%, and after treatment with the pre-lithiation solution containing additives for 24 hours was 85%. This shows that the pre-lithiation performance of the pre-lithiation solution containing additives is well maintained.

[0094] The novel chemical pre-lithiation solution proposed in this invention has the advantages of good stability and long storage time. By slowing down the failure of the chemical pre-lithiation solution with additives, in addition to improving the stability of the chemical pre-lithiation solution, it can also reduce production costs. It eliminates the need for frequent preparation of fresh chemical pre-lithiation solution during production, thereby increasing the utilization rate of the chemical pre-lithiation solution. This also reduces the proportion of failed and discarded chemical pre-lithiation solutions, reducing pollutant emissions and effectively mitigating pollution caused by ether reagents and aromatic hydrocarbon compounds.

[0095] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for improving the stability of a chemically pre-lithiated solution, characterized in that, The method includes: A chemical pre-lithiation solution is prepared with lithium metal using ether solvents and aromatic hydrocarbon compounds. An additive containing anion X is added simultaneously with or after the preparation of the chemical pre-lithiation solution to form the final chemical pre-lithiation solution. The anion in the additive containing anion X is anion X that has coordination ability with lithium ions. This allows the anion X in the additive to participate in the coordination structure in the chemical pre-lithiation solution, thereby stabilizing the lithium ions in the chemical pre-lithiation solution and mitigating the disproportionation reaction of its effective component Li1A during storage, which forms a coordination structure between aromatic hydrocarbon anions and more than one lithium ion. y The generation of A; wherein, 1 < y ≤ 6, and the Li1A is a complex formed by the aromatic hydrocarbon anion A and lithium ions; The additive containing anion X is a soluble lithium salt or a soluble sodium salt.

2. The method according to claim 1, characterized in that, The soluble lithium salts include one or more combinations of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethyl)sulfonyl)imide (LiTFSI), lithium perchlorate (LiClO4), lithium nitrate (LiNO3), lithium difluorooxalate borate (LiODFB), lithium dioxalate borate (LiBOB), and lithium borohydride (LiBH4).

3. The method according to claim 1, characterized in that, The soluble sodium salt includes NaPF6.

4. The method according to claim 1, characterized in that, In the chemically pre-lithiated solution, the concentration of the additive containing anion X is 0.001 mol / L to 10 mol / L.

5. The method according to claim 1, characterized in that, The main chain of the ether solvent is composed of carbon atoms and oxygen atoms, and may contain one or more substituents.

6. The method according to claim 5, characterized in that, The ether solvents include one or more of the following: ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, and tetrahydropyran.

7. The method according to claim 1, characterized in that, The aromatic hydrocarbon compound contains one or more benzene rings, and the benzene rings may or may not contain substituents.

8. The method according to claim 7, characterized in that, The aromatic hydrocarbons include one or more of naphthalene and its derivatives, biphenyl and its derivatives, and phenanthrene and its derivatives.

9. A chemically pre-lithiated solution, characterized in that, The chemically prelithiated solution is obtained by the method for improving the stability of the chemically prelithiated solution as described in any one of claims 1-8.

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