Pre-lithiated pole piece surface passivation treatment method, obtained pre-lithiated pole piece and electronic equipment

Abstract

The invention discloses a pre-lithiated pole piece surface passivation treatment method, an obtained pre-lithiated pole piece and electronic equipment, and belongs to the technical field of electrode material processing. The preparation method comprises the following steps: firstly, dissolving multifunctional small molecules containing acidic groups and alkaline groups into a non-protonic solvent to obtain a passivation treatment solution, and then soaking the pre-lithiated pole piece into the passivation treatment solution until the surface passivation treatment is completed, so that the pre-lithiated pole piece can be prepared by adopting a calendering lithium supplement mode or an evaporation lithium supplement mode; byproducts such as LiOH, Li2CO3 and the like, which react with air, on the surface of the pre-lithiated negative plate are subjected to passivation treatment and then are subjected to in-situ conversion into a passivation layer participating in formation of an SEI film. Experiments show that compared with a battery prepared from an untreated pole piece, the lithium ion battery prepared from the pre-lithium negative pole piece subjected to passivation treatment has the advantages that the hardness of SEI is improved, the direct-current internal resistance of a battery cell and the full-charge expansion rate of the battery cell are reduced at the same time, and finally the technical effects of improving the first effect of the battery and prolonging the service life of the battery are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrode material processing, and in particular relates to a surface passivation treatment method for a pre-lithium electrode sheet and the obtained pre-lithium electrode sheet and electronic equipment. Background Art

[0002] With the rapid development of electric vehicles, energy storage power stations and other fields, the demand for lithium-ion batteries continues to increase, and at the same time, higher requirements are placed on their performance. Silicon negative electrode materials can provide higher capacitance and longer cycle life compared to traditional graphite negative electrode materials due to their advantages such as high theoretical capacity and low lithium insertion and deinsertion potential. It is considered to be a potential new generation of lithium-ion battery negative electrode materials. However, the traditional silicon negative electrode material will form a solid electrolyte membrane (Solid Electrolyte Interface, SEI) during the cycle process, which consumes a large amount of active lithium ions, resulting in a decrease in the battery's first coulombic efficiency and a decrease in gram capacity. At present, a pre-lithium replenishment process is often used to pretreat the negative electrode sheet to avoid capacity loss caused by the consumption of a large amount of active lithium ions.

[0003] By pre-adding lithium to the silicon negative electrode in advance so that it does not consume lithium from the positive electrode, the problem of reduced initial coulombic efficiency and reduced gram capacity of the battery can be alleviated to a certain extent. However, pre-lithium (lithium replenishment) also brings new problems. Due to the extremely strong activity of lithium, the lithium on the surface of the pre-lithium electrode easily reacts with oxygen, nitrogen, water vapor and carbon dioxide in the air, which directly leads to the accumulation of by-products such as residual lithium and residual alkali (such as LiOH, Li2CO3, etc.) on the surface of the electrode. These by-products cannot be used in subsequent electrochemical reactions, so they are also called "dead alkali" and "dead lithium". In addition, these by-products greatly reduce the utilization rate of the lithium replenishment layer. The corresponding loss of lithium replenishment efficiency will make the first effect of the battery less than expected and the battery energy density insufficient.

[0004] Therefore, during the pre-lithiation process, additives are often used to suppress the formation of dead alkali and dead lithium, such as using low concentrations of lithium salts or other electrolyte salts, controlling the roughness of the electrode surface, and optimizing the composition and concentration of the electrolyte. In addition, some post-treatment technologies are also used to remove byproducts such as residual lithium and residual alkali on the electrode surface, such as ultrasonic cleaning and electrolyte exchange. However, these treatment methods also have certain problems and are not satisfactory. Summary of the Invention

[0005] To address the problems of existing pre-lithiation methods, the present invention provides a method for passivating the surface of a pre-lithiation electrode sheet. Using this method to treat a pre-lithiation electrode sheet can improve the initial efficiency and cycle life of the battery. The present invention also provides a pre-lithiation electrode sheet, electrochemical device, and electronic device obtained using the aforementioned method.

[0006] In order to solve the problems of the prior art, the technical solutions of the present invention are as follows:

[0007] A method for passivating the surface of a pre-lithium electrode comprises dissolving a multifunctional small molecule in an organic solvent to obtain a passivation treatment solution, and immersing the pre-lithium electrode in the passivation treatment solution until the surface passivation treatment is completed. The multifunctional small molecule is a compound having a structure of Formula I:

[0008]

[0009] Among them, F1, F2, and F3 are independently selected from one of amino groups and amide groups; one of C2-C8 alkenyl groups and diene groups; or one of sulfonic acid groups, sulfonic acid alkyl groups, sulfonamide groups, benzylcarboxyl groups, hydroxyl groups, phenolic hydroxyl groups, and sulfate groups; n1, n2, and n3 are integers of 1 to 3, preferably 1.

[0010] Furthermore, in the compound of formula I, the amine group is or The amide is: R1, R2, R, R' are C1-C6 linear / branched alkyl, or C1-C6 fluorinated linear / branched alkyl;

[0011] The C2-C10 alkenyl group is: or The sulfonic acid group is: -SO3H, and the sulfonic acid alkyl group is R3 is a C1-C6 straight chain / branched alkyl group, in some embodiments The benzyl carboxyl group is: -C6H4COOH, the phenolic hydroxyl group is: -C6H4OH, and the sulfate group is -OSO2O-.

[0012] In some embodiments of the present invention, in the compound of formula I,

[0013] Among them, F1 is vinyl; F2 is Wherein R, R' are H or C1-C6 linear / branched alkyl; F3 is -C6H4COOH, sulfonamide phenyl, -OH or -SO3H; n1, n2, n3 are 1.

[0014] Furthermore, the multifunctional small molecule is specifically one or more of 2-acrylamide-2-methylpropanesulfonic acid, 4-acrylamide-benzoic acid, N-[4-(sulfonamide)phenyl]acrylamide, N-(hydroxymethyl)acrylamide, and 3-acrylamide-phenol.

[0015] Furthermore, the organic solvent is one or more of fluoroether, diethyl ether, and tetrahydrofuran.

[0016] Furthermore, in the surface passivation treatment method for the pre-lithium electrode sheet, the pre-lithium electrode sheet is a pre-lithium negative electrode sheet prepared by rolling lithium replenishment or evaporation lithium replenishment.

[0017] Furthermore, after the pre-lithium electrode is passivated, it is cleaned and dried.

[0018] Furthermore, the content of the compound used to passivate the pre-lithium electrode in the passivation solution is 0.1-10 wt%.

[0019] Furthermore, in the pre-lithium electrode surface passivation treatment method, the period of time is specifically 10s to 5min.

[0020] Furthermore, the pre-lithium amount of the pre-lithium electrode is k mg / cm 2 When the concentration of the multifunctional small molecule for passivating the pre-lithium electrode in the passivation treatment solution is t wt%, t=k*(0.5-5), t and k are numbers greater than 0.

[0021] A pre-lithium electrode sheet treated by any of the above-described passivation treatment methods for pre-lithium electrode sheets.

[0022] An electrochemical device comprises a pre-lithium electrode plate treated by a passivation treatment method for a pre-lithium electrode plate.

[0023] An electronic device comprises the electrochemical device.

[0024] Compared with the prior art, this application has at least the following beneficial effects:

[0025] The present invention uses a passivation treatment solution containing multifunctional small molecules to treat the electrode after lithium supplementation. The multifunctional small molecules react with the residual lithium and residual alkali on the surface of the pre-lithium electrode, eliminate the residual lithium and residual alkali in the pre-lithium process through chemical reaction, and convert the residual lithium and residual alkali generated in the pre-lithium process into an inert and dense passivation layer to isolate the air and reduce the occurrence of side reactions. Since the passivation layer converted from residual lithium and residual alkali can participate in the formation of lithium-conducting SEI, the utilization efficiency of lithium is improved and the amount of pre-lithium can be reduced. The passivation treatment solution of the present invention plays the role of turning waste into treasure, and the SEI formed has higher conductivity. According to tests, the pre-lithium negative electrode sheet passivated by the present invention is prepared into a lithium-ion battery. Compared with the battery prepared by the untreated electrode sheet, it can effectively reduce the DC internal resistance of the battery cell and the full charge expansion rate of the battery cell, and significantly improve the first efficiency of the battery and increase the cycle life of the battery. Therefore, the present invention has good application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the process flow for passivation treatment of pre-lithium electrode;

[0027] Figure 2This is a comparison of the surface byproduct detection of the pre-lithium electrode after passivation treatment and the pre-lithium electrode without passivation treatment. A and B show the peaks of Li2CO3 and lithium nitrogen compounds respectively;

[0028] Figure 3 This is an electron microscope image of the surface morphology and microstructure of the pre-lithium electrode without passivation treatment;

[0029] Figure 4 This is an electron microscope image of the surface morphology and microstructure of the pre-lithium electrode after passivation treatment. DETAILED DESCRIPTION

[0030] The following is a preferred implementation of the embodiments of the present application. It should be noted that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the embodiments of the present application. These improvements and modifications are also considered to be within the scope of protection of the embodiments of the present application.

[0031] For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and similarly, any upper limit can be combined with any other upper limit to form an unspecified range. In addition, although not explicitly stated, each point or individual value between the endpoints of a range is included in the range. Thus, each point or individual value can serve as its own lower limit or upper limit and be combined with any other point or individual value, or with other lower limits or upper limits, to form an unspecified range.

[0032] In the description of this article, it should be noted that, unless otherwise specified, “above” and “below” are inclusive of the number themselves, and “a variety” in “one or more” means more than two.

[0033] The above disclosure of the present application is not intended to describe every disclosed embodiment or every implementation in the present application. The following description more specifically illustrates exemplary embodiments. In many places throughout the application, guidance is provided through a series of examples, which can be used in various combinations. In each example, the enumeration is intended only as a representative group and should not be construed as exhaustive.

[0034] In the present application, the pre-lithium electrode sheet is also called the pre-lithiation electrode sheet, which includes an electrode sheet and a metallic lithium layer composited on the electrode sheet, and the metallic lithium layer is used to replenish lithium to the active material layer on the electrode sheet.

[0035] In some specific implementations, the lithium-supplementing electrode sheet is a lithium-supplementing negative electrode sheet, comprising a negative electrode sheet and a metallic lithium layer composited on the negative electrode sheet.

[0036] In some specific implementations, the negative electrode sheet includes a pole sheet and a negative electrode active layer composited on one side of the pole sheet, the negative electrode active layer includes a negative electrode active material, and the negative electrode active material is selected from one or more of carbon materials, silicon-based materials, metallic lithium or lithium alloys; the metallic lithium layer is composited on the negative electrode active layer.

[0037] The present application has no special limitation on the electrode piece, and any current collector well known to those skilled in the art can be used, such as a copper foil with a thickness of 8 μm.

[0038] In some specific implementations, the negative electrode active layer includes a negative electrode active material, a conductive agent and a binder, wherein the negative electrode active material includes but is not limited to one or more of carbon materials, silicon-based materials, metallic lithium or lithium alloys, preferably one or both of graphite or silicon-based materials, for example, graphite / silicon composite materials; the conductive agent includes but is not limited to one or more of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber; the binder includes but is not limited to one or more of styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyethylene oxide (PEO), etc. and their lithium salt substitutes.

[0039] In some specific implementations, the negative electrode active layer can be provided on one side or both sides of the electrode piece, and correspondingly, the lithium metal layer is also provided on one side or both sides of the electrode piece.

[0040] The present invention has no requirements or limitations on the form of pre-lithiation or lithium supplementation, and any existing technology can be used to pre-lithiate or supplement the negative electrode sheet.

[0041] In some specific implementations, the metal lithium layer can be composited on the negative electrode active layer by rolling or evaporation. The present application has no particular restrictions on the rolling or evaporation method, and the process parameters well known to those skilled in the art can be used. In some specific implementations, the surface density of the metal lithium layer is obtained, which is calculated as M mg / cm 2 .

[0042] The present application first pre-treats the pre-lithium electrode in a passivation treatment solution, wherein the passivation treatment solution includes a multifunctional small molecule and an organic solvent. In some specific implementations, the multifunctional small molecule has the following structure:

[0043]

[0044] Among them, F1, F2, and F3 are independently selected from one of an amino group and an amide group; one of a C2-C10 alkenyl group and a diene group; or one of a sulfonic acid group, a sulfonic acid alkyl group, a sulfonamide phenyl group, a benzylcarboxyl group, a hydroxyl group, a phenolic hydroxyl group, and a sulfate group; n1, n2, and n3 are integers of 1 to 3, preferably 1.

[0045] In some specific implementations, in the compound of formula I, the amine group is or The amide is: R1, R2, R, R' are H or C1-C6 linear / branched alkyl, or C1-C6 fluorinated linear / branched alkyl;

[0046] The C2-C10 alkenyl group is: or The sulfonic acid group is: -SO3H, and the sulfonic acid alkyl group is R3 is a C1-C6 straight chain / branched alkyl group, in some embodiments The benzyl carboxyl group is: -C6H4COOH, the phenolic hydroxyl group is: -C6H4OH, and the sulfate group is -OSO2O-.

[0047] In some embodiments of the present invention, in the compound of formula I, F1 is vinyl; F2 is Wherein R, R' are H or C1-C6 linear / branched alkyl; F3 is -C6H4COOH, sulfonamide phenyl, -OH or -SO3H; n1, n2, n3 are 1.

[0048] In the multifunctional small molecule, the acidic group reacts with residual lithium and residual alkali to consume these pre-lithium byproducts. The basic group can be used to regulate the reaction activity of the acidic group with residual lithium and residual alkali, and the acidic group and the basic group can improve the ion conductivity of the reaction product. The double-bonded carbon chain segment is conducive to the formation of polymer products, improves the strength of the product, makes it more dense, and has a passivation effect.

[0049] In some specific implementations, by adjusting the values of n1 and n3 and screening different F1 and F3 functional groups, the pH value of the small molecule can be adjusted to match electrodes with different pre-lithiation amounts.

[0050] In some specific implementations, the multifunctional small molecule is one or more of 2-acrylamide-2-methylpropanesulfonic acid (AMPS), 4-acrylamide-benzoic acid, N-[4-(sulfonamide)phenyl]acrylamide, N-(hydroxymethyl)acrylamide, and 3-acrylamide-phenol.

[0051] In some specific implementations, the solvent of the passivation treatment solution is fluoroether, diethyl ether, tetrahydrofuran, etc., and the concentration of the multifunctional small molecule in the solvent can be 0.1-10 wt%.

[0052] In some specific implementations, n1=n2=n3=1, such as AMPS.

[0053] In some specific implementations, different pre-lithiation amounts (area density k mg / cm 2 ) is added to a fluoroether solution of a functional small molecule with a concentration of t wt%, t = k*(0.5-5), and more preferably, t = k*1.2.

[0054] In this application, the effect of using a passivation treatment solution to treat the pre-lithium electrode is that the multifunctional small molecules in the passivation treatment solution can react with residual alkali and residual lithium to form a passivation layer. Taking the fluoroether solution of the multifunctional small molecule AMPS as the passivation treatment solution as an example, the fluoroether solution of AMPS can react with residual lithium and residual alkali to generate 2-acrylamide-2-methylpropanesulfonic lithium and LiF in situ and become a passivation layer. The passivation layer blocks the air from further reacting with metallic lithium and can stop the passivation reaction spontaneously. In addition, the passivation layer participates in the formation of the subsequent SEI film, which can improve the use efficiency of the pre-lithium and improve the performance of the SEI film, ultimately improving the first efficiency and cycle performance of the battery.

[0055] In this application, in some specific implementations, the specific method of treating the pre-lithium electrode with the passivation treatment solution can be (eg Figure 1 shown):

[0056] Step 1: Prepare a multifunctional small molecule solution of appropriate concentration: Select a multifunctional small molecule that meets the above requirements, weigh an appropriate weight, add it to a solvent, and shear it at high speed to dissolve and evenly disperse it, as a passivation treatment solution;

[0057] Step 2: The rolled electrode with lithium supplementation is rewound through a passivation treatment liquid tank, a cleaning solution tank, and a drying oven to complete the treatment steps.

[0058] For further optimization, step 2 can be repeated n times, such as 3 times, and the same or different concentrations of passivation treatment solution can be used each time to improve the uniformity of the treatment interface.

[0059] In some specific implementations, the method for treating the pre-lithium electrode with the passivation solution may also be:

[0060] Step 1: Prepare a functional small molecule solution of appropriate concentration: Select a functional small molecule that meets the requirements of the claims, weigh an appropriate amount, add it to a solvent, and shear it at high speed to dissolve and evenly disperse it;

[0061] Step 2: Use a die cutter to die-cut the pre-lithium treated electrode into sheets;

[0062] Step 3: Clamp the tab with a clamp and immerse the die-cut electrode piece in the passivation treatment solution obtained in step 1, accompanied by slight vibration. After 8 seconds to 5 minutes of treatment time, take it out and dry it;

[0063] For further optimization, step 3 can be repeated n times, such as 3 times, and the same or different concentrations of passivation treatment solution can be used each time to improve the uniformity of the treatment interface.

[0064] The passivation method for the pre-lithium electrode provided by the present application and its technical effects are described in detail below with reference to the embodiments. Those skilled in the art will understand that the preparation method described in this application is only an example, and any other suitable preparation method is within the scope of this application.

[0065] Example 1:

[0066] 1. Preparation of pre-lithium negative electrode sheet: the pre-lithium amount is 3mg / cm2 according to the following rolling lithium replenishment method 2 Pole piece:

[0067] Weigh the negative electrode active material (artificial graphite / Si composite), binder (polyacrylic acid PAA), and conductive carbon fibers in a weight ratio of 95:4:1. Thoroughly stir and mix these materials in an appropriate amount of deionized water until a uniform negative electrode slurry is formed. Apply this slurry evenly to one side of the negative electrode current collector copper foil. After coating, dry and cold-press the coated copper foil to obtain the negative electrode sheet.

[0068] Then, take the surface density as 3mg / cm 2 The lithium metal foil is then transferred to the prepared negative electrode sheet using a roller pressing process under strictly controlled environmental conditions. During this process, the dew point of the environment is always kept below -40°C, resulting in a pre-lithium negative electrode sheet.

[0069] 2. Passivation treatment of pre-lithium negative electrode

[0070] (1) Preparation of a 2 wt% passivation treatment solution: 2-acrylamide-2-methylpropanesulfonic acid (AMPS) was weighed and added to a fluoroether solvent, and the solution was dissolved and evenly dispersed by high-speed shearing to prepare a 2 wt% passivation treatment solution;

[0071] (2) The lithium-supplemented electrode is rewound and passivated for 10 seconds in a passivation solution tank containing 2 wt% passivation solution, then cleaned in a cleaning solution tank containing dimethyl carbonate (DMC), and finally dried in a drying oven to complete the pre-lithium electrode passivation treatment step.

[0072] Example 2:

[0073] 1. Preparation of pre-lithium negative electrode sheet: prepare the pre-lithium amount to 2mg / cm according to the following evaporation lithium replenishment method 2 Pole piece:

[0074] Weigh the negative electrode active material (artificial graphite / Si composite), binder (polyacrylic acid PAA), and conductive carbon fibers in a weight ratio of 95:4:1. Thoroughly stir and mix these materials in an appropriate amount of deionized water until a uniform negative electrode slurry is formed. Apply this slurry evenly to one side of the negative electrode current collector copper foil. After coating, dry and cold-press the coated copper foil to obtain the negative electrode sheet.

[0075] Then, the initial negative electrode sheet is placed in the vacuum chamber through the transmission mechanism, and the lithium source metal is placed in the lithium source evaporator. When the vacuum degree in the vacuum chamber reaches 5×10 -2 After the pressure drops below Pa, the lithium source metal continues to melt and evaporate in the lithium source evaporator to form metal vapor. The lithium metal vapor is deposited on the surface of the initial negative electrode to form a lithium replenishment layer. The thickness of the lithium replenishment layer is controlled to be 2μm to 3μm. The negative electrode after lithium replenishment is then left to stand at a dew point of -40°C for 24 hours.

[0076] 2. Passivation treatment of pre-lithium negative electrode

[0077] (1) Preparation of a 1.5 wt% passivation treatment solution: 2-acrylamide-2-methylpropanesulfonic acid was weighed and added to a fluoroether solvent, and high-speed shearing was performed to dissolve and uniformly disperse the 2-acrylamide-2-methylpropanesulfonic acid to prepare a 1.5 wt% passivation treatment solution;

[0078] (2) The lithium-supplemented electrode is rewound and passivated for 8 seconds in a passivation treatment tank containing 1.5 wt% passivation treatment solution, then cleaned in a tank containing ethylene glycol dimethyl ether (DME) cleaning solution, and finally dried in a drying oven to complete the pre-lithium electrode passivation treatment step.

[0079] Comparative Example 1:

[0080] Compared with Example 1, the step of “2. passivation treatment of pre-lithium negative electrode sheet” is not included, and the remaining steps are the same.

[0081] Comparative Example 2:

[0082] Compared with Example 2, the step of “2. passivation treatment of pre-lithium negative electrode sheet” is not included, and the remaining steps are the same.

[0083] Example 3: Battery Assembly and Testing

[0084] 1. Assembling lithium-ion batteries

[0085] The specific method is as follows:

[0086] (1) Electrolyte

[0087] Commercially purchased lithium battery electrolyte.

[0088] (2) Preparation of lithium-supplemented negative electrode sheets

[0089] The pre-lithium negative electrode sheet after passivation treatment prepared according to Example 1-2 and the pre-lithium negative electrode sheet without passivation treatment prepared according to the method in Comparative Example 1-2.

[0090] (3) Preparation of positive electrode sheet

[0091] Lithium cobalt oxide (LiCoO2), a conductive agent (Super P), and polyvinylidene fluoride are weighed in a predetermined mass ratio, mixed, and added to an N-methylpyrrolidone (NMP) solvent. A vacuum mixer is used to mix the mixture to create a positive electrode slurry. The slurry is then evenly coated onto the positive electrode current collector aluminum foil. The cathode sheet is then dried, cold-pressed, cut, slit, and the tabs are welded to the sheet.

[0092] (4) Isolation film

[0093] A polyethylene (PE) isolation membrane coated with a PVDF adhesive layer and an Al2O3 ceramic layer is used.

[0094] (5) Preparation of lithium-ion batteries

[0095] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, ensuring that the separator is positioned precisely between the positive and negative electrodes to provide effective isolation. This three-layer structure is then wound to form a bare cell. Next, the bare cell is placed in an outer aluminum-plastic film packaging, and the previously prepared electrolyte is injected into the dried bare cell. Finally, after vacuum packaging, room-temperature and high-temperature static polymerization, high-temperature formation, and shaping, the lithium-ion battery is assembled.

[0096] 2. Performance test of passivation treatment electrode and lithium-ion battery:

[0097] The pre-lithium electrode sheets prepared in Example 1-2 and Comparative Example 1-2 were directly subjected to XPS testing and sample preparation, and electron microscope photography was completed. After the pre-lithium electrode sheets prepared in Example 1-2 and Comparative Example 1-2 were assembled into lithium-ion batteries, the batteries were tested for the first cycle coulomb efficiency test, the cell DC resistance test, and the full charge expansion rate test. Then, a portion of the cells that had completed the first charge and discharge were disassembled, and some of the negative electrode sheets were cut for sample preparation, and the SEI Young's modulus measurement was completed. The undisassembled lithium-ion batteries continued to be charged and discharged until the cell life test was completed. The following are the main contents and results of each test:

[0098] 1. XPS test

[0099] The pre-lithium negative electrode sheet prepared in Example 1 and the pre-lithium negative electrode sheet prepared in Comparative Example 1 were analyzed by X-ray photoelectron spectroscopy on the surface of the negative electrode sheet before and after lithium supplementation. The element distribution in the area from the surface of the negative electrode sheet to a depth of 1 μm was determined by XPS point scanning along the thickness direction of the negative electrode sheet. The results are as follows: Figure 2 As shown, Figure 2 The results show that the peaks of Li2CO3 and lithium nitrogen compounds are greatly reduced, indicating that the treated electrode can effectively eliminate residual alkali and lithium components such as Li2CO3 on the surface of the pre-lithium electrode.

[0100] 2. Electron microscope photography

[0101] Take the pre-lithium negative electrode sheet passivated in Example 1 and the pre-lithium negative electrode sheet prepared in Comparative Example 1, and take pictures using a field emission scanning electron microscope SU8010. The microscopic morphology of the surface of the negative electrode sheet is shown in the figure below. Figure 3 and Figure 4 As shown in the figure, the contour clarity of the pre-lithium electrode particles that have not been passivated is low, and the surface of the particles is covered with numerous particles of uneven size, sharp edges, and loose and porous; while the by-product layer on the surface of the pre-lithium electrode after passivation disappears, and the surface of the particles is covered with a thin dense layer.

[0102] 3. First cycle coulombic efficiency (first efficiency of battery cell) test

[0103] The lithium-ion battery was charged at 0.2C at 25°C to the charge cutoff voltage, then charged at a constant voltage until the current dropped to approximately 0.025C. The battery was then discharged at a 0.2C rate to the discharge cutoff voltage to obtain the initial charge and discharge capacities. Initial coulombic efficiency = initial discharge capacity / initial charge capacity.

[0104] 4. Full charge expansion rate test

[0105] The initial thickness of the lithium-ion battery measured with a micrometer is H0, and the thickness of the lithium-ion battery measured after the first charge and discharge is H1. Full charge expansion rate = (H1-H0) / H0×100%.

[0106] 5. DC resistance of battery cell

[0107] Discharge the battery cells at a constant current of 0.1C for 10 seconds, then change the current to 1C for 1 second. Calculate the DC resistance of the battery cells based on the ratio of the rate of change of voltage to the rate of change of current during the discharge process.

[0108] 6. SEI Young's modulus test

[0109] Atomic force microscopy (AFM) was used to measure the Young's modulus of the SEI film on the surface of the pre-lithium electrode sheets prepared in Examples 1-2 and Comparative Examples 1-2. The AFM probe was fixed to a cantilever beam with a certain degree of elasticity, so the deformation of the cantilever beam can be used to reflect the mechanical properties of the sample. A force curve was constructed by comparing the relationship between the force applied to the sample and the sample deformation. The Young's modulus of the SEI film was then obtained using the force curve information. In this experiment, the Young's modulus of the outermost layer of the SEI film was statistically analyzed, and the results are shown in Table 1 (for specific detection methods, please refer to publicly reported literature).

[0110] 7. Battery life test

[0111] A lithium-ion battery is cycled through full charge and discharge cycles until its storage capacity drops to 80% of its original value. One charge and discharge cycle (charging to the battery's rated maximum charge voltage and discharging to the battery's rated minimum discharge voltage) is called a cycle, represented by a circle.

[0112] Table 1 Lithium-ion battery performance test results

[0113]

[0114] Table 1 shows the performance test results of lithium-ion battery cells prepared from lithium-ion battery negative electrode sheets that have been passivated and those that have not been passivated. The battery negative electrode sheets in Example 1 and Example 2 were treated with passivation treatment solutions with concentrations of 2wt% and 1.5wt%, respectively. The test results show that compared with Example 1 and Comparative Example 1, which use the same rolling lithium supplementation method, the battery cell of Example 1, which adds the passivation treatment step, has a certain degree of decrease in the DC internal resistance and the full charge expansion rate of the battery cell, while the SEI modulus has increased by more than 2 times, the battery cell life has increased by 36%, and the battery cell first efficiency has reached 90%. Similar changes can be seen when comparing Comparative Example 2 and Example 2, which use the same evaporation lithium supplementation method. Although the battery cell of Example 2, which adds the passivation treatment step, has no significant change in the full charge expansion rate, the DC internal resistance of the battery cell has decreased by 11%, its SEI Young's modulus has increased by more than 1.6 times, the battery cell life has increased by 40%, and the battery cell first efficiency has reached 91%. Therefore, the overall performance of the battery has also been significantly improved. Comparing the above test results shows that adding a passivation treatment step can reduce residual alkali and lithium in the negative electrode sheet, thereby increasing the SEI hardness and conductivity, and reducing the full-charge expansion rate of the battery cell, ultimately achieving the technical effects of improving the initial efficiency and battery life. Therefore, the present invention has achieved significant technical progress.

[0115] The present application provides an electrochemical device comprising the above-mentioned passivation-treated pre-lithium electrode, as an optional technical solution of the present application. The electrochemical device of the present application includes, but is not limited to: all types of primary batteries, secondary batteries, fuel cells, solar cells or capacitors.

[0116] As an optional technical solution of the present application, the electrochemical device is a lithium secondary battery, wherein the lithium secondary battery includes but is not limited to: a lithium metal secondary battery, a lithium ion battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery.

[0117] The present application also provides electronic devices comprising an electrochemical device of a passivated pre-lithium electrode, as optional technical solutions of the present application, including, but not limited to: laptop computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, electric vehicles or lithium-ion capacitors, etc.

Claims

1. A method for passivation treatment of the surface of a pre-lithium electrode, characterized in that: The multifunctional small molecule is dissolved in an organic solvent to obtain a passivation treatment solution, and the pre-lithium electrode is immersed in the passivation treatment solution until the surface passivation treatment is completed. The multifunctional small molecule is a compound with a structure of formula I: Wherein, F1, F2, and F3 are independently selected from one of an amino group and an amide group; one of a C2-C8 alkenyl group and a diene group; or one of a sulfonic acid group, a sulfonic acid alkyl group, a sulfonamide group, a benzylcarboxyl group, a hydroxyl group, a phenolic hydroxyl group, and a sulfate group; and n1, n2, and n3 are integers of 1 to 3.

2. The method for surface passivation treatment of a pre-lithium electrode according to claim 1, characterized in that: In the compound of formula I, the amine group is or The amide is: R1, R2, R, R' are H or C1-C6 straight chain / branched alkyl, or C1-C6 fluorinated straight chain / branched alkyl; the C2-C10 alkenyl is: or The sulfonic acid group is: -SO3H, and the sulfonic acid alkyl group is R3 is a C1-C6 straight chain / branched alkyl group, the benzyl carboxyl group is: -C6H4COOH, the phenolic hydroxyl group is: -C6H4OH, and the sulfate group is -OSO2O-.

3. The method for surface passivation treatment of a pre-lithium electrode according to claim 1, characterized in that: In the compound of formula I, Among them, F1 is vinyl; F2 is Wherein R, R' are H or C1-C6 linear / branched alkyl; F3 is -C6H4COOH, sulfonamide phenyl, -OH or -SO3H; n1, n2, n3 are 1.

4. The method for surface passivation treatment of a pre-lithium electrode according to claim 1, characterized in that: The multifunctional small molecule is specifically one or more of 2-acrylamide-2-methylpropanesulfonic acid, 4-acrylamide-benzoic acid, N-[4-(sulfonamide)phenyl]acrylamide, N-(hydroxymethyl)acrylamide, and 3-acrylamide-phenol.

5. The method for surface passivation treatment of a pre-lithium electrode according to claim 1, characterized in that: The organic solvent is one or more of fluoroether, diethyl ether and tetrahydrofuran.

6. The method for surface passivation treatment of a pre-lithium electrode according to claim 1, characterized in that: The pre-lithium electrode sheet is a pre-lithium negative electrode sheet prepared by rolling lithium supplementation or evaporation lithium supplementation.

7. The method for surface passivation treatment of a pre-lithium electrode according to claim 1, characterized in that: After the passivation treatment of the pre-lithium electrode is completed, cleaning and drying are continued.

8. The method for surface passivation treatment of a pre-lithium electrode according to claim 1, characterized in that: The concentration of the multifunctional small molecules in the passivation treatment solution is 0.1-10 wt%.

9. The method for surface passivation treatment of a pre-lithium electrode according to claim 1, characterized in that: The passivation treatment time is specifically 8s to 5min.

10. The method for surface passivation treatment of a pre-lithium electrode according to claim 1, characterized in that: The pre-lithium amount of the pre-lithium electrode is k mg / cm 2 When the concentration of the multifunctional small molecules used to passivate the pre-lithium electrode in the passivation treatment solution is twt%, t=k*(0.5~5), and k and t are numbers greater than 0.

11. A pre-lithium electrode sheet obtained by the surface passivation treatment method of a pre-lithium electrode sheet according to any one of claims 1 to 10.

12. An electrochemical device, characterized in that Including the pre-lithium electrode according to claim 11.

13. The electrochemical device according to claim 12, characterized in that The electrochemical device is a lithium-ion battery.

14. An electronic device, characterized in that: It comprises the electrochemical device according to claim 13.

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