Method for forming artificial SEI membrane through chemical passivation of pre-lithiated negative electrode of aqueous battery and application of artificial SEI membrane

Abstract

The embodiment of the invention relates to a method for forming an artificial SEI membrane through chemical passivation of a pre-lithiated negative electrode of an aqueous battery and application. The method comprises the following steps: performing chemical pre-lithiation on an aqueous battery cathode active substance A or a cathode pole piece containing the cathode active substance A in a lithium supplement agent, so that the cathode active substance A is converted into a lithium-intercalated cathode active substance LiXA; placing the lithium-intercalated negative electrode active material LiXA or a negative electrode plate containing the lithium-intercalated negative electrode active material LiXA in the air for standing, forming an artificial solid electrolyte interface SEI membrane by utilizing self-discharge of the lithium-intercalated negative electrode active material LiXA, and reducing the negative electrode active material A at the same time; the process of forming the solid electrolyte interface SEI through self discharge comprises one, two or all of # imgabs 0 # imgabs 1 # 4LixA + 2xCO2 + xO2-> 2xLi2CO3 + 4A and # imgabs 2 # 2LixA + 2xH2O-> xH2 + 2xLiOH + 2A.

Description

Technical Field

[0001] The present invention relates to the technical field of aqueous batteries, and in particular to a method and application of chemical passivation of a pre-lithiation negative electrode of an aqueous battery to form an artificial SEI film. Background Art

[0002] Aqueous batteries have the advantages of simple manufacturing environment, environmental friendliness, and intrinsic safety. However, due to the narrow window of aqueous electrolytes, the battery cycle inevitably faces the problem of hydrogen evolution, resulting in poor cycle performance. In order to weaken the hydrogen evolution reaction and extend the battery life, the existence of a solid electrolyte interphase (SEI) membrane is very critical. Existing artificial SEI technologies, such as coating, vapor deposition, and atomic layer deposition, are time-consuming and labor-intensive, costly, and difficult to mass produce.

[0003] Chinese invention patent application CN 109802109 A discloses a method for pre-lithiation of silicon-based negative electrode of battery and simultaneous formation of SEI film. The main method is to mix inert lithium powder in solvent A to form solution A. 1-fluorodecane is uniformly mixed in solvent B to form solution B. Silicon oxide is added to solution B so that 1-fluorodecane is uniformly wrapped on the surface of silicon oxide to form solution C. A and C are mixed to form solution D. Inert lithium powder in solution D reacts with 1-fluorodecane on the surface of silicon oxide to form SEI film coated on the surface of silicon oxide, and the surface of silicon oxide is pre-lithiated. The reactants of the artificial SEI in this patent application are surface-coated 1-fluorodecane and lithium powder. SEI is formed by reaction in solution. It is a method of modifying the surface coating layer after coating. The method is supplemented by stirring and heating. The method is not simple, and its negative electrode material is in lithium-intercalated state. Similarly, Chinese invention patent application CN 116487574 A discloses a method for pre-lithiation and artificial SEI of silicon-based negative electrode materials. The artificial SEI of this patent application comes from the electrolyte containing the fluorine-containing additive heptafluoropropyl 1,2,2,2-tetrafluoroethyl ether. Similarly, pre-lithiation of the negative electrode is also one of its purposes. The application objects of the above two patent applications are silicon-based negative electrodes, which are completely unsuitable for aqueous batteries due to potential reasons.

[0004] Chinese invention patent application CN 114678494 A discloses a method for pre-lithiation of a negative electrode and obtaining an SE I film at the same time. The main method of this patent application is to attach a metal lithium sheet to the surface of the negative electrode plate, then bake the pre-lithiated negative electrode and introduce a reaction gas to react, so as to obtain a pre-lithiated negative electrode plate with an SE I film on the surface. In the pre-lithiation process, the pre-lithiation method of this patent application is to attach a metal lithium layer to the surface of the negative electrode, rather than inserting lithium into the negative electrode. The final pre-lithiation step of this patent application is formed by the metal lithium layer, and SE I is formed by the reaction of the metal lithium layer on the surface of the negative electrode and the introduced gas, that is, the reactant is metal lithium. No matter what the negative electrode under the metal lithium layer is, the reaction principle is the reaction of metal lithium and gas. Therefore, this patent application has specific requirements for dew point, vacuum degree, reaction temperature, gas purity, gas introduction amount, etc., and the actual operation is cumbersome to achieve the reaction of the metal lithium layer and the high-purity formulated gas. Moreover, in this patent, the amount of lithium replenished per unit area of ​​negative electrode is limited to (negative electrode capacity per unit area - positive electrode capacity per unit area × NP) / (theoretical gram capacity of metallic lithium × 80%), wherein the NP ratio ranges from 1 to 1.5, which means that the negative electrode capacity is assumed to be greater than the positive electrode capacity, and points out that a too small NP value will lead to lithium precipitation, which only occurs in organic lithium-ion battery systems, and is common in conventional organic lithium-ion battery system negative electrodes such as graphite. Summary of the invention

[0005] The purpose of the present invention is to provide a method and application of chemical passivation of aqueous battery pre-lithiation negative electrode to form artificial SE I film, and to convert negative electrode active material A into lithium-intercalated negative electrode active material Li by chemical pre-lithiation or electrochemical pre-lithiation. X A, and then use the principle that the lithium-embedded negative electrode active material has a low potential and can spontaneously react with oxygen, carbon dioxide, water vapor and other gases in the air, and self-discharge when left standing in the air to form an artificial SE I layer.

[0006] To this end, in a first aspect, an embodiment of the present invention provides a method for chemically passivating a pre-lithiation negative electrode of an aqueous battery to form an artificial SE I film, the method comprising:

[0007] The negative electrode active material A of the aqueous battery or the negative electrode sheet containing the negative electrode active material A is placed in a lithium supplement agent for chemical pre-lithiation, so that the negative electrode active material A is converted into a lithium-inserted negative electrode active material Li X A;

[0008] The lithium-intercalated negative electrode active material Li X A or contains lithium-intercalated negative electrode active material Li X The negative electrode plate of A is placed in the air and allowed to stand. XThe self-discharge of A forms an artificial solid electrolyte interface SEI film, and at the same time reduces the negative electrode active material A;

[0009] The process of self-discharge to form a solid electrolyte interface SEI includes: 4Li x A+2xCO2+xO2→2xLi2CO3+4A, 2Li x One, two or all of A+2xH2O→=xH2+2xLiOH+2A.

[0010] Preferably, the lithium supplement agent specifically comprises: an organic lithium reagent containing electron-deficient properties;

[0011] The electron-deficient organic lithium reagent includes: solutions of methyl lithium, butyl lithium, naphthyl lithium, biphenyl lithium, lithium borohydride and other organic compounds with lithium-carbon (Li-C) bonds, and solutions of derivatives; wherein the concentration of the organic lithium reagent does not exceed 10M.

[0012] Preferably, the degree of lithium insertion in the negative electrode does not exceed 100%, that is, the capacity of chemical pre-lithiation does not exceed the theoretical capacity of the negative electrode active material A of the aqueous battery.

[0013] Preferably, the standing time in the air is sufficient until the negative electrode active material is converted from the lithium-embedded negative electrode active material Li X A completes self-discharge and returns to a state without lithium insertion.

[0014] Preferably, the chemical pre-lithiation specifically includes:

[0015] The negative electrode active material A of the aqueous battery or the negative electrode sheet containing the negative electrode active material A is placed in the lithium supplement for 1 minute to 24 hours;

[0016] Among them, the mass concentration of the lithium replenisher is C, the volume is V, the amount of lithium inserted per mole of the lithium replenisher is xmol, the mass of the negative electrode active material A is M, and the amount of lithium ion inserted per unit mass to reach the theoretical capacity is ymol, xCV=zMy, wherein z is the percentage of the pre-lithiation capacity to the theoretical capacity of the negative electrode, 0<z≤1, and z is positively correlated with the amount of artificial SEI film formed.

[0017] In a second aspect, the present invention provides a method for chemically passivating a pre-lithiation negative electrode of an aqueous battery to form an artificial SEI film, the method comprising:

[0018] Electrochemical pre-lithiation of the negative electrode sheet containing the negative electrode active material A of the aqueous battery is performed to convert the negative electrode active material A into a lithium-inserted negative electrode active material Li X A;

[0019] The negative electrode active material Li X The negative electrode plate of A is placed in the air and allowed to stand. X The self-discharge of A forms a solid electrolyte interface SEI and reduces the negative electrode active material A at the same time;

[0020] The process of self-discharge to form a solid electrolyte interface SEI includes: 4Li x A+2xCO2+xO2→2xLi2CO3+4A, 2Li x One, two or all of A+2xH2O→xH2+2xLiOH+2A.

[0021] Preferably, after the electrochemical pre-lithiation, the degree of lithium insertion in the negative electrode does not exceed 100%, that is, the capacity of the electrochemical pre-lithiation does not exceed the theoretical capacity of the negative electrode active material A of the aqueous battery.

[0022] Preferably, the standing time in the air is sufficient until the negative electrode active material is converted from the lithium-embedded negative electrode active material Li X A completes self-discharge and returns to a state without lithium insertion.

[0023] Preferably, the electrochemical pre-lithiation specifically includes:

[0024] The negative electrode sheet containing the negative electrode active material A of the aqueous battery is placed in an electrolytic cell, and the negative electrode is charged using the oxidized sacrificial material as the positive electrode, and the charging capacity is not higher than the theoretical capacity of the negative electrode.

[0025] In a third aspect, an embodiment of the present invention provides an artificial SEI film formed by chemical passivation of a pre-lithiation negative electrode of an aqueous battery, prepared according to the method for chemical passivation of a pre-lithiation negative electrode of an aqueous battery as described in the first or second aspect above.

[0026] In a fourth aspect, an embodiment of the present invention provides an aqueous battery negative electrode comprising an artificial SEI film formed by chemical passivation of the aqueous battery pre-lithiation negative electrode as described in the third aspect above.

[0027] In a fifth aspect, an embodiment of the present invention provides an aqueous secondary battery comprising the aqueous battery negative electrode described in the fourth aspect.

[0028] The method for chemically passivating the pre-lithiation negative electrode of an aqueous battery to form an artificial SEI film provided by the embodiment of the present invention can act on a negative electrode active material in a powder state or on a prepared negative electrode plate. The method is flexible in its action object, making the patent widely applicable. By chemical pre-lithiation, the negative electrode active material A is converted into a lithium-inserted negative electrode active material LiX A, and then take advantage of the low potential of the active material of the lithium-intercalated negative electrode, which can spontaneously react with gases such as oxygen, carbon dioxide, and water vapor in the air, and self-discharge when left standing in the air to form an artificial SE I layer. The implementation conditions of the present invention are simple, and the negative electrode after pre-lithiation can be directly left standing in the air. There is no requirement for the environment, no need for heating, no need to control the dew point, and no need to pass gas. The operation is simple and easy, and it can be prepared and used on a large scale. This method is suitable for conventional negative electrodes of aqueous batteries. There is no problem of lithium metal precipitation during the process. It is applied to aqueous batteries, and there is no restriction on the positive electrode material on the opposite side; the amount of lithium replenishment by chemical pre-lithiation is easy to control and is not affected by the NP value (the ratio of the negative electrode capacity to the sum of the positive electrode capacity and the lithium replenishment capacity). All lithium content of the lithium-intercalated negative electrode caused by pre-lithiation is completely converted into lithium compounds in the SE I component during the self-discharge process.

[0029] Compared with vapor deposition, atomic layer deposition, coating and other methods, the method provided by the present invention has lower cost, simpler operation and wider application scenarios. The lithium carbonate, lithium oxide and lithium hydroxide formed by self-discharge are stable in nature, which is conducive to inhibiting side reactions in the battery cycle, thereby improving the cycle life of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A flow chart of a method for chemically passivating a pre-lithiation negative electrode of an aqueous battery to form an artificial SE I film provided by an embodiment of the present invention;

[0031] Figure 2 A flow chart of another method for chemically passivating a pre-lithiation negative electrode of an aqueous battery to form an artificial SE I film provided by an embodiment of the present invention;

[0032] Figure 3 A schematic diagram of the preparation process of chemical passivation of the pre-lithiation negative electrode of an aqueous battery to form an artificial SE I film provided by an embodiment of the present invention;

[0033] Figure 4 This is a transmission electron microscopy (TEM) image of the artificial SE I prepared in Example 1 of the present invention;

[0034] Figure 5 TEM image of artificial SE I prepared in Example 2 of the present invention;

[0035] Figure 6 This is a comparison chart of the x-ray photoelectron spectroscopy (XPS) before and after preparing the artificial SE I in Example 3 of the present invention;

[0036] Figure 7 Cycle-specific capacity curves of an aqueous battery with a lithium manganese oxide positive electrode provided in Example 4 of the present invention and a TiO2 negative electrode that is chemically passivated after pre-lithiation to form an artificial SEI film, and an aqueous battery provided in Comparative Example 1. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

[0038] The embodiment of the present invention provides a method for forming an artificial SEI film by chemical passivation of a pre-lithiated negative electrode of an aqueous battery, which can be achieved by chemical pre-lithiation or electrochemical pre-lithiation after the negative electrode active material is intercalated with lithium, and then the intercalated negative electrode active material is allowed to self-discharge in the air. The two methods are described below.

[0039] Method 1: The embodiment of the present invention provides a method for chemically passivating the pre-lithiation negative electrode of an aqueous battery to form an artificial SEI film based on a chemical pre-lithiation method. The main steps are as follows: Figure 1 As shown, including:

[0040] Step 110, placing the negative electrode active material A of the aqueous battery or the negative electrode sheet containing the negative electrode active material A in a lithium supplement agent for chemical pre-lithiation, so that the negative electrode active material A is converted into a lithium-inserted negative electrode active material Li X A.

[0041] Among them, the lithium supplement agent is specifically: an organic lithium reagent containing electron-deficient properties; the organic lithium reagent containing electron-deficient properties includes: methyl lithium, butyl lithium, naphthyl lithium, biphenyl lithium, lithium borohydride and other organic compounds with lithium-carbon (Li-C) bonds, and solutions of derivatives; wherein the concentration of the organic lithium reagent does not exceed 10M.

[0042] The specific operation method is: place the negative electrode active material A of the aqueous battery or the negative electrode plate containing the negative electrode active material A in the lithium supplement agent for 1 minute to 24 hours. The mass concentration of the lithium supplement agent is C, the volume is V, the amount of lithium inserted per mole of the lithium supplement agent is x mol, the mass of the negative electrode active material A is M, and the amount of lithium ion inserted per unit mass when the lithium is fully inserted to reach the theoretical capacity is y mol, which must satisfy xCV=zMy, where z is the percentage of the pre-lithiation capacity to the theoretical capacity of the negative electrode, 0<z≤1, and z is positively correlated with the amount of artificial SEI film formed. In the actual implementation of the technical solution of the present invention, the value of z can be preset by the technician according to actual needs.

[0043] After chemical pre-lithiation, the negative electrode active material or electrode is placed in n-hexane, heptane, benzene, ethylene glycol dimethyl ether, butyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, etc., a solvent that is volatile and not easy to react with the lithium-intercalated negative electrode and lithium replenishing reagent, to remove the residual reagent on the surface, and then taken out and dried.

[0044] After chemical pre-lithiation, the degree of lithium insertion in the negative electrode does not exceed 100%, that is, the capacity of chemical pre-lithiation does not exceed the theoretical capacity of the negative electrode active material A of the aqueous battery.

[0045] Step 120, inserting lithium-embedded negative electrode active material Li X A or contains lithium-intercalated negative electrode active material Li X The negative electrode plate of A is placed in the air and allowed to stand. X The self-discharge of A forms an artificial solid electrolyte interface SEI film and reduces the negative electrode active material A at the same time.

[0046] There is no limit to the time of standing in the air. From the beginning of standing, the lithium-embedded negative electrode active material Li X A self-discharges to form a solid electrolyte interface, and the standing time is sufficient until the negative electrode active material is transformed from the lithium-embedded negative electrode active material Li X A completes self-discharge and returns to a state without lithium insertion. The electrochemical performance is almost no discharge capacity. The time of standing in the air in the experiment of the present invention is 1-7 days, and the standing time in each of the following embodiments varies from 1 to 3 days.

[0047] The process of self-discharge to form a solid electrolyte interface (SEI) includes: 4Li x A+2xCO2+xO2→2xLi2CO3+4A, 2Li x One, two or all of A+2xH2O→xH2+2xLiOH+2A.

[0048] For aqueous batteries other than aqueous lithium-ion batteries, such as aqueous sodium-ion batteries, the method of this patent can still be applied.

[0049] This method can also be applied to aqueous sodium ion batteries / aqueous zinc ion batteries, etc., to chemically passivate the pre-sodium / pre-zinc negative electrode to form an artificial SEI. Taking aqueous sodium ion batteries as an example, the chemical pre-lithiation method of step 110 is replaced by chemical pre-sodiumization, wherein the chemical pre-sodiumization reagent uses an organic sodium reagent containing electron-deficient properties, such as a solution of organic sodium compounds such as sodium naphthyl, sodium biphenyl, sodium dibenzophenone, and their derivatives.

[0050] Method 2: The embodiment of the present invention provides a method for forming an artificial SEI film by chemically passivating the negative electrode of an aqueous battery pre-lithiation based on an electrochemical pre-lithiation method. The main steps are as follows: Figure 2 As shown, including:

[0051] Step 210, electrochemically pre-lithiate the negative electrode sheet containing the negative electrode active material A of the aqueous battery to convert the negative electrode active material A into a lithium-inserted negative electrode active material LiX A.

[0052] The specific operation method is: placing the negative electrode sheet containing the negative electrode active material A of the aqueous battery into the electrolytic cell, charging the negative electrode with the oxidized sacrificial material as the positive electrode, and the charging capacity does not exceed the theoretical capacity of the negative electrode. The oxidized sacrificial material can be commonly used in the prior art, such as the positive electrode of a lithium-ion battery, easily corroded metal anode aluminum, copper, etc., and is not specifically limited here.

[0053] After electrochemical pre-lithiation, the negative electrode active material is placed in a solvent such as n-hexane, heptane, benzene, ethylene glycol dimethyl ether, butyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, etc., which is volatile and not easy to react with the lithium-intercalated negative electrode and lithium replenishing reagent, to remove the residual reagent on the surface, and then taken out and dried.

[0054] After electrochemical pre-lithiation, the degree of lithium insertion in the negative electrode does not exceed 100%, that is, the capacity of the electrochemical pre-lithiation does not exceed the theoretical capacity of the negative electrode active material A of the aqueous battery.

[0055] Step 220, containing lithium-embedded negative electrode active material Li X The negative electrode plate of A is placed in the air and allowed to stand. X The self-discharge of A forms a solid electrolyte interface SEI and reduces the negative electrode active material A at the same time.

[0056] There is no limit to the time of standing in the air. From the beginning of standing, the lithium-embedded negative electrode active material Li X A self-discharges to form a solid electrolyte interface, and the standing time is sufficient until the negative electrode active material is transformed from the lithium-embedded negative electrode active material Li X A completes self-discharge and returns to a state without lithium insertion. The electrochemical performance is almost no discharge capacity. The time of standing in the air in the experiment of the present invention is 1-7 days, and the standing time in each of the following embodiments varies from 1 to 3 days.

[0057] The process of self-discharge to form a solid electrolyte interface (SEI) includes: 4Li x A+2xCO2+xO2→2xLi2CO3+4A, 2Li x One, two or all of A+2xH2O→xH2+2xLiOH+2A.

[0058] This method can also be applied to chemical passivation of pre-sodium / zinc negative electrodes in aqueous sodium / zinc ion batteries to form artificial SEI.

[0059] Figure 3The schematic diagram of the preparation process of chemical passivation of the pre-lithiation negative electrode of the aqueous battery to form an artificial SEI film provided in the embodiment of the present invention can be used to help those skilled in the art to understand the process of the present invention more intuitively.

[0060] In the two methods proposed above, the negative electrode active material A can be a common negative electrode active material of aqueous battery lithium ion battery, such as TiO2, Mo6S8, Li4Ti5O 12 ,LiV3O8,LiTi2(PO4)3,TiP2O7, etc.

[0061] If it is used in aqueous sodium ion batteries, the negative electrode can be NaTi2(PO4)3, V2O5, VO2, NaV6O 15 wait.

[0062] In the above two methods of the present invention, it is proposed to place the negative electrode plate in the air and let it stand for self-discharge. However, those skilled in the art know from the process of self-discharge to form a solid electrolyte interface (SEI) disclosed in the above invention that self-discharge to form a solid electrolyte interface can also occur in a single oxygen environment or in an environment containing carbon dioxide, water vapor, etc. or in water.

[0063] The artificial SEI film formed by chemical passivation of the pre-lithiation negative electrode of the aqueous battery prepared by the above method can be applied to the negative electrode of the aqueous secondary battery.

[0064] The method for chemically passivating the pre-lithiation negative electrode of an aqueous battery to form an artificial SEI film provided by the embodiment of the present invention can act on a negative electrode active material in a powder state or on a prepared negative electrode plate. The method is flexible in acting on the object, making the patent widely applicable. By chemical pre-lithiation or electrochemical pre-lithiation, the negative electrode active material A is converted into a lithium-inserted negative electrode active material Li X A, and then take advantage of the low potential of the active material of the lithium-intercalated negative electrode, which can spontaneously react with oxygen, carbon dioxide, water vapor and other gases in the air, and self-discharge when left standing in the air to form an artificial SEI layer. The implementation conditions of the present invention are simple, and the negative electrode after pre-lithiation can be directly left standing in the air. There is no requirement for the environment, no need for heating, no need to control the dew point, and no need to pass gas. The operation is simple and easy, and it can be prepared and used on a large scale. This method is suitable for conventional negative electrodes of aqueous batteries. There is no problem of lithium metal precipitation during the process. It is applied to aqueous batteries, and there is no restriction on the opposite positive electrode material; the amount of lithium replenishment by chemical pre-lithiation is easy to control and is not affected by the NP value (the ratio of the negative electrode capacity to the sum of the positive electrode capacity and the lithium replenishment capacity). All lithium content of the lithium-intercalated negative electrode caused by pre-lithiation is completely converted into lithium compounds in the SE I component during the self-discharge process.

[0065] In order to more clearly illustrate the purpose and advantages of the present invention, the present invention is further described below in conjunction with the embodiments. In addition, the embodiments described in the present invention are only partial embodiments. Based on the embodiments described in the present invention, all other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present invention. In addition, it should be understood that these embodiments are only used for more detailed description and should not be understood as limiting the present invention in any form, that is, they are not intended to limit the protection scope of the present invention.

[0066] Example 1

[0067] This embodiment provides a method for preparing an artificial SE I: 1 g of titanium dioxide powder is soaked in 16 mL of 0.8 M butyl lithium n-hexane solution for 10 min to pre-lithiate the titanium dioxide powder. The pre-lithiated material is taken out, fully washed with n-hexane, and allowed to stand in air for 72 hours before TEM testing. Figure 4 This is a picture obtained by TEM test after the powdered titanium dioxide was pre-lithiated by chemical pre-lithiation method and self-discharged in air to form SE I. Figure 4 As shown, it can be clearly seen that there are lithium oxide and lithium carbonate lattices near the titanium dioxide lattice, indicating that this method successfully forms an artificial SE I on the negative electrode material titanium dioxide.

[0068] Example 2

[0069] This example provides a method for preparing an artificial SE I: 2 The titanium dioxide electrode with an area of ​​4.3×5.6 cm was immersed in 8 ml of 0.8 M butyl lithium n-hexane solution for 10 min, washed three times with n-hexane, and left to stand in the air for 72 hours before TEM testing. Figure 5 This is a picture obtained after TEM testing of the titanium dioxide pole piece after self-discharge in the air to form SE I using the chemical pre-lithiation method. Figure 5 As shown, it can be clearly seen that there is a lithium carbonate lattice near the titanium dioxide lattice, indicating that this method successfully forms an artificial SE I on the negative electrode titanium dioxide pole piece.

[0070] Example 3

[0071] This example provides a method for preparing an artificial SE I: 2, a titanium dioxide pole piece with a diameter of 12 mm was immersed in 10 ml of 0.8 M butyl lithium n-hexane solution for 10 minutes, then washed three times with a total of 20 ml of n-hexane, left to stand in the air for 72 hours, and then subjected to XPS testing. The two pole pieces were finely scanned by the X-ray electron energy spectra of C1s and Li1s, and the results are shown in Figure 6. It can be seen that after the titanium dioxide pole piece was pre-lithiated to form an artificial SEI, strong peaks of lithium carbonate and lithium oxide appeared. In the C1s spectrum in the figure, the peak signal at 291eV of the pole piece that formed an artificial SEI after pre-lithiation represents the appearance of lithium carbonate. At the same time, in the Li1s spectrum, new peak signals appeared at 55eV and 55.4eV, representing the components of lithium carbonate and lithium oxide, respectively. The above experiments show that this method successfully formed an artificial SEI on the negative titanium dioxide pole piece.

[0072] Example 4

[0073] This embodiment provides a LiMn2O4-TiO2 aqueous battery device and a method for extending the cycle life, wherein the method of chemically passivating the TiO2 negative electrode after pre-lithiation to form an artificial SEI film is achieved by pre-lithiating the prepared electrode by chemical pre-lithiation. The preparation process of the LiMn2O4-TiO2 aqueous battery device specifically includes:

[0074] Preparation of positive electrode: The positive electrode active material is lithium manganate LiMn2O4. The positive electrode active material LiMn2O4, the conductive additive carbon black, and the polyvinylidene fluoride (PVDF) binder are weighed in a mass ratio of 8:1:1, wherein PVDF exists in the form of being dissolved in N-methylpyrrolidone (NMP) solution. After the positive electrode active material and the conductive additive are fully ground, PVDF is added, and after high-speed uniform mixing in a mixer, the slurry is evenly coated on aluminum foil. After being completely dried, the positive electrode is obtained using a slicing mechanism.

[0075] Preparation of negative electrode: Titanium dioxide TiO2 is selected as the negative electrode material. The negative electrode active material TiO2, the conductive additive carbon black, and the water-based binder polyacrylate are weighed according to the mass ratio of 8:1:1, wherein the water-based binder exists in the form of being dissolved in water. After the active material and the conductive additive are fully ground, the water-based binder is added, and the slurry is evenly coated on the aluminum foil after high-speed uniform mixing in the mixer. After being completely dried, the negative electrode is obtained by using a slicing mechanism. After the negative electrode is prepared, the mass of the negative electrode active material is 3g. After soaking it in 50ml of 0.8M butyl lithium n-hexane solution for 10min, its lithium insertion amount is about 100% of the theoretical capacity. It is washed three times with a total of 150ml of n-hexane and left to stand in the air for 72 hours.

[0076] The battery was assembled according to a mass ratio of the active materials of the positive electrode to the negative electrode of 2:1.

[0077] Electrolyte system: The electrolyte is a 10m (mass molar concentration, unit mol / kg) lithium bis(trifluoromethanesulfonyl)imide LiTFSI solution, and the solvent is water.

[0078] The capacity of the aqueous battery device of this embodiment is approximately 0.5 Ah.

[0079] The test uses constant current charge and discharge test, with a rate of 1C and a charge and discharge voltage of 0.5V-2.5V.

[0080] Comparative Example 1

[0081] This comparative example provides an aqueous battery, in which the positive electrode, negative electrode, electrolyte, separator and assembly method are the same as those in Example 4, except that the negative electrode in the aqueous battery of this comparative example does not undergo a process of self-discharging in air after pre-lithiation.

[0082] The conditions of the cycle test of this comparative example are the same as those of Example 4.

[0083] After the water-based batteries of Example 4 and Comparative Example 1 were cycled, the cycle capacity curves were as follows: Figure 7 As shown, it can be seen that Example 4 uses a negative electrode treated with the artificial SEI of the present invention, which is better than Comparative Example 1 in capacity retention, especially in coulombic efficiency. Since the artificial SEI suppresses the hydrogen evolution side reaction, the coulombic efficiency of Example 4 is much better than that of Comparative Example 1. This example illustrates that the preparation method of the artificial SEI provided by the present invention can be beneficial to suppressing side reactions in battery cycling, thereby improving the cycling performance of the battery.

[0084] Example 5

[0085] This embodiment provides a method for forming an artificial SEI by chemically passivating the negative electrode of a Mo6S8 aqueous lithium-ion battery after pre-lithiation. In this embodiment, a chemical pre-lithiation method is used to pre-lithiate the powder material to form an SEI film, and then the treated powder is used to make the electrode. The preparation process of the Mo6S8 aqueous battery negative electrode containing an artificial SEI layer specifically includes:

[0086] The process of chemical passivation of negative electrode powder after pre-lithiation to form artificial SEI: 5g Mo6S8 powder was immersed in 10mL 1M biphenyl lithium ethylene glycol dimethyl ether solution and stirred for 10 minutes to form its lithium state Li x Mo6S8, where x is about 1.3, is then washed three times with a total of 50 ml of ethylene glycol dimethyl ether, and the obtained electrode is left to stand in the air for 24 hours to obtain Mo6S8 powder with artificial SEI formed on the surface after self-discharge.

[0087] Preparation of negative electrode sheet: Mo6S8 powder that has been pre-lithiated to form artificial SEI is selected as the negative electrode material. Mo6S8, conductive additive carbon black, and binder polyvinylidene fluoride (PVDF) are weighed in a mass ratio of 8:1:1. After the active material and conductive additive are fully ground, PVDF is added. After high-speed uniform mixing in a mixer, the slurry is evenly coated on aluminum foil. After it is completely dried, the negative electrode is obtained using a slicing mechanism.

[0088] In this embodiment, the Mo6S8 active material powder is first pre-lithiated by a chemical pre-lithiation method, and then left to stand in air to form an artificial SEI before preparing the electrode. The capacity retention rate and coulombic efficiency of the obtained electrode during the battery cycle are much better than those of the Mo6S8 electrode that has not undergone this pre-lithiation treatment.

[0089] Example 6

[0090] This embodiment provides a Li4Ti5O 12 A method for forming an artificial SEI by chemically passivating the negative electrode of an aqueous lithium-ion battery after pre-lithiation. In this embodiment, the prepared electrode is pre-lithiated by an electrochemical pre-lithiation method and then left to stand in the air to form a SEI film. The preparation process specifically includes:

[0091] Preparation of negative electrode sheet: Li4Ti5O is used as negative electrode material 12 , weigh the negative electrode active material Li4Ti5O according to the mass ratio of 8:1:1 12 , conductive additive carbon black, and binder polyvinylidene fluoride (PVDF). After grinding the active material and conductive additive thoroughly, add PVDF, mix them evenly at high speed in a mixer, and evenly apply the slurry on aluminum foil. After it is completely dried, use a slicing mechanism to obtain the negative electrode.

[0092] Pre-lithiation and artificial SEI film formation method: Take 20mL LiTFSI solution in a beaker and mix Li4Ti5O 12 The negative electrode is connected to the negative electrode of the charge and discharge tester, and the positive electrode is the common lithium-ion battery positive electrode LiCoO2 electrode connected to the positive electrode of the charge and discharge tester. The positive and negative electrodes are placed in a beaker containing 20mLiTFSI solution at the same time, and then the negative electrode Li4Ti5O is charged by constant current 1C. 12 The electrode is charged until the capacity reaches 80% of the theoretical capacity. After electrochemical pre-lithiation, the negative electrode is quickly removed and washed three times in n-hexane to remove the original electrolyte, and then left in the air for 3 days. The n-hexane evaporates quickly, and then the lithium-embedded Li4Ti5O 12 The electrode reacts with the atmosphere in the air to form an artificial SEI film.

[0093] In this example, the prepared Li4Ti5O 12The negative electrode is pre-lithiated by electrochemical pre-lithiation and then left in air to form an artificial SEI film. The capacity retention rate and coulomb efficiency of the treated electrode are much better than those of Li4Ti5O2 without pre-lithiation treatment in battery cycle. 12 Negative electrode.

[0094] The method of the present invention should also be applicable to aqueous sodium ion batteries, etc. A specific example is given below.

[0095] Example 7

[0096] This embodiment provides a method for forming an artificial SEI by chemically passivating the negative electrode of a NaTi2(PO4)3 aqueous sodium ion battery after pre-sodiumization. In this embodiment, a chemical pre-sodiumization method is used to pre-sodiumize the powder material to form an SEI film, and then the treated powder is used to make the electrode. The preparation process of the NaTi2(PO4)3 aqueous battery negative electrode containing an artificial SEI layer specifically includes:

[0097] The process of chemical passivation of the negative electrode powder after pre-sodiumization to form an artificial SEI: 1g NaTi2(PO4)3 powder is soaked in 2.5mL of 0.6M sodium naphthyl in ethylene glycol dimethyl ether solution for 10 minutes to obtain a negative electrode material powder with a sodium embedding amount of about 60% of the theoretical capacity, and then washed three times with a total of 15ml of ethylene glycol dimethyl ether. The obtained powder is left to stand in the air for 48 hours to obtain NaTi2(PO4)3 powder that has been pre-sodiumized to form an artificial SEI.

[0098] Preparation of negative electrode sheet: The negative electrode material is NaTi2(PO4)3 powder that has been pre-sodiumized to form artificial SEI. The negative electrode active material NaTi2(PO4)3, conductive additive carbon black, and binder sodium alginate are weighed in a mass ratio of 8:1:1. After the active material and conductive additive are fully ground, the sodium alginate binder is added. After high-speed uniform mixing in a mixer, the slurry is evenly coated on aluminum foil. After it is completely dried, the negative electrode is obtained using a slicing mechanism.

[0099] In this embodiment, the NaTi2(PO4)3 active material powder is first pre-sodiumized by a chemical pre-sodiumization method, and then left to stand in air to form an artificial SEI before preparing an electrode. The capacity retention rate and coulombic efficiency of the obtained electrode during the battery cycle are much better than those of the NaTi2(PO4)3 electrode that has not undergone this pre-sodiumization treatment.

[0100] It can be seen that the method for chemically passivating the pre-lithiation negative electrode of the aqueous battery to form an artificial SEI film provided by the embodiment of the present invention can act on the negative electrode active material in a powder state or on the prepared negative electrode sheet. The flexibility of the method's action object enables this patent to be widely used.

[0101] By chemical pre-lithiation or electrochemical pre-lithiation, the negative electrode active material A is converted into a lithium-inserted negative electrode active material Li X A, and then take advantage of the low potential of the active material of the lithium-intercalated negative electrode, which can spontaneously react with gases such as oxygen, carbon dioxide, and water vapor in the air, and self-discharge in the air to form an artificial SE I layer. The implementation conditions of the present invention are simple, and the pre-lithiation negative electrode can be directly left in the air. There is no requirement for the environment, no need for heating, no need to control the dew point, and no need to pass gas. The operation is simple and easy, and it can be prepared and used on a large scale. This method is suitable for conventional negative electrodes of aqueous batteries. There is no problem of lithium metal precipitation during the process. It is applied to aqueous batteries, and there is no restriction on the positive electrode material on the opposite side; the amount of lithium replenishment by chemical pre-lithiation is easy to control and is not affected by the NP value (the ratio of the negative electrode capacity to the sum of the positive electrode capacity and the lithium replenishment capacity). All lithium content of the lithium-intercalated negative electrode caused by pre-lithiation is completely converted into lithium compounds in the SE I component during the self-discharge process. This method can also be extended to battery systems such as aqueous sodium ion batteries or aqueous zinc ion batteries.

[0102] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method 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 in the scope of protection of the present invention.

Claims

1. A method for chemically passivating a pre-lithiation negative electrode of an aqueous battery to form an artificial SE I film, characterized in that: The method comprises: The negative electrode active material A of the aqueous battery or the negative electrode sheet containing the negative electrode active material A is placed in a lithium supplement agent for chemical pre-lithiation, so that the negative electrode active material A is converted into a lithium-inserted negative electrode active material Li X A; The lithium-intercalated negative electrode active material Li X A or contains lithium-inserted negative electrode active material Li X The negative electrode plate of A is placed in the air and allowed to stand. X The self-discharge of A forms an artificial solid electrolyte interface SEI film, and at the same time reduces the negative electrode active material A; The process of self-discharge to form a solid electrolyte interface SEI includes: 4Li x A+2xCO2+xO2→2xLi2CO3+4A, 2Li x One, two or all of A+2xH2O→xH2+2xLiOH+2A.

2. The method according to claim 1, characterized in that The lithium supplement agent specifically comprises: an organic lithium reagent having electron-deficient properties; The electron-deficient organic lithium reagent includes: solutions of methyl lithium, butyl lithium, naphthyl lithium, biphenyl lithium, lithium borohydride and other organic compounds with lithium-carbon (Li-C) bonds, and solutions of derivatives; wherein the concentration of the organic lithium reagent does not exceed 10M.

3. The method according to claim 1, characterized in that After the chemical pre-lithiation, the degree of lithium insertion in the negative electrode does not exceed 100%, that is, the capacity of the chemical pre-lithiation does not exceed the theoretical capacity of the negative electrode active material A of the aqueous battery.

4. The method according to claim 1, characterized in that: The standing time in the air is sufficient until the negative electrode active material is transformed from the lithium-embedded negative electrode active material Li X A completes self-discharge and returns to a state without lithium insertion.

5. The method according to claim 1, characterized in that The chemical pre-lithiation specifically includes: Placing the negative electrode active material A of the aqueous battery or the negative electrode sheet containing the negative electrode active material A in the lithium supplement for 1 minute to 24 hours; Among them, the mass concentration of the lithium replenisher is C, the volume is V, the amount of lithium inserted per mole of the lithium replenisher is x mol, the mass of the negative electrode active material A is M, and the amount of lithium ion insertion required for complete lithium insertion per unit mass to reach the theoretical capacity is y mol, xCV=zMy, wherein z is the percentage of the pre-lithiation capacity to the theoretical capacity of the negative electrode, 0<z≤1, and z is positively correlated with the amount of artificial SEI film formed.

6. A method for chemically passivating a pre-lithiated negative electrode of an aqueous battery to form an artificial SEI film, characterized in that: The method comprises: Electrochemical pre-lithiation of the negative electrode sheet containing the negative electrode active material A of the aqueous battery is performed to convert the negative electrode active material A into a lithium-inserted negative electrode active material Li X A; The negative electrode active material Li X The negative electrode plate of A is placed in the air and allowed to stand. X The self-discharge of A forms a solid electrolyte interface SEI and reduces the negative electrode active material A at the same time; The process of self-discharge to form a solid electrolyte interface SEI includes: 4Li x A+2xCO2+xO2→2xLi2CO3+4A, 2Li x One, two or all of A+2xH2O→xH2+2xLiOH+2A.

7. The method according to claim 6, characterized in that After the electrochemical pre-lithiation, the degree of lithium insertion in the negative electrode does not exceed 100%, that is, the capacity of the electrochemical pre-lithiation does not exceed the theoretical capacity of the negative electrode active material A of the aqueous battery.

8. The method according to claim 6, characterized in that The standing time in the air is sufficient until the negative electrode active material is transformed from the lithium-embedded negative electrode active material Li X A completes self-discharge and returns to a state without lithium insertion.

9. The method according to claim 6, characterized in that The electrochemical pre-lithiation specifically comprises: The negative electrode sheet containing the negative electrode active material A of the aqueous battery is placed in an electrolytic cell, and the negative electrode is charged using the oxidized sacrificial material as the positive electrode, and the charging capacity is not higher than the theoretical capacity of the negative electrode.

10. An artificial SEI film formed by chemical passivation of an aqueous battery pre-lithiation negative electrode prepared according to the method for chemical passivation of an aqueous battery pre-lithiation negative electrode to form an artificial SEI film as described in claims 1-5 or 6-9.

11. An aqueous battery negative electrode comprising an artificial SEI film formed by chemical passivation of the aqueous battery pre-lithiation negative electrode as claimed in claim 10.

12. An aqueous secondary battery comprising the aqueous battery negative electrode according to claim 11.

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