Method for testing the integrity of prelithiated silicon-oxygen negative electrode material by electrolyte immersion

Abstract

The application belongs to the field of detection methods, and discloses a method for testing the coating integrity of pre-lithiated silicon-oxygen negative electrode material by electrolyte soaking. The pre-lithiated silicon-oxygen negative electrode material is soaked by electrolyte, and the color change and characterization test are observed, so that whether the coating of the pre-lithiated silicon-oxygen negative electrode material is complete and dense is accurately evaluated. The method can more accurately judge the inhibition effect of the pre-lithiated silicon-oxygen negative electrode material on the penetration of the electrolyte, and whether the content of the residual alkaline substance on the surface will affect the electrolyte.

Description

Technical Field

[0001] This invention belongs to the technical field of detection methods, and particularly relates to a method for inspecting the coating integrity of pre-lithiated silicon-oxygen anode materials by immersion in electrolyte. Background Technology

[0002] With the development of technology, the demand for high-energy-density lithium-ion batteries is increasing. Currently, the specific capacity of widely used graphite-based anode materials has approached its theoretical value (372 mAh / g), leaving little room for further improvement. Silicon-oxygen anode materials, due to their relatively low expansion (150%-200%) and long cycle life, are easier to mass-produce and apply. However, the presence of some oxygen in silicon-oxygen anode materials leads to the consumption of active lithium during the initial lithium intercalation process, resulting in a low initial coulombic efficiency. Therefore, improving the initial coulombic efficiency of silicon-oxygen anode materials is of significant research importance.

[0003] Currently, pre-lithiation technology is considered the optimal method to improve the initial coulombic efficiency of silicon-oxygen anode materials. The essence of pre-lithiation is to utilize a lithium source (LiH, Li₂CO₃, LiOH, etc.) to react with SiO₂ in the silicon-oxygen anode material beforehand to generate lithium silicates (Li₄SiO₄, Li₂SiO₃, Li₂Si₂O₅), thus avoiding the consumption of active lithium in the battery and improving the initial coulombic efficiency. Specifically, using LiH as the lithium source for pre-lithiation of the silicon-oxygen anode material can achieve an initial coulombic efficiency of over 90%.

[0004] However, because pre-lithiated silicon-oxygen anode materials are modified using lithium sources, residual Li2O remains on the carbon layer surface after the reaction. When exposed to air, this Li2O reacts with oxygen, water, and carbon dioxide to form Li2CO3 and LiOH, resulting in a high overall alkalinity (pH > 12) in the aqueous slurry during the slurry preparation process. Therefore, during homogenization, the alkaline solution penetrates into the carbon layer and reacts with the silicon grains, producing hydrogen gas and causing a gas generation reaction in the slurry. Furthermore, the alkaline substances on the surface of the pre-lithiated silicon-oxygen anode material can also cause electrolyte decomposition and gas generation, affecting lithium-ion transport and posing a safety hazard. During battery cycling, the electrolyte also penetrates into the carbon layer and reacts with the silicon grains to form Li2SiF6, leading to capacity decay.

[0005] To address the defects in pre-lithiated silicon-oxygen anode materials, current methods primarily focus on improving the coating integrity of the pre-lithiated silicon-oxygen anode material surface through back-end coating. This helps suppress gas generation reactions and prevent the penetration of alkaline solutions and electrolytes. However, research on methods for verifying the coating integrity of pre-lithiated silicon-oxygen anode materials is currently limited. Therefore, accurately evaluating the coating integrity of each material is crucial during the testing and screening of anode materials, especially as it provides significant reference for the safety and lifespan of the material in subsequent battery applications.

[0006] Patent document CN201910594116.5 discloses a method for accurately measuring the gas production of a silicon anode in a lithium-ion battery, comprising the following steps: 1) preparing the components of a slurry; 2) mixing and ball-milling the components of the slurry; 3) pre-weighing an aluminum-plastic film bag, then filling the ball-milled slurry into the aluminum-plastic film bag and weighing it again; 4) partially evacuating the aluminum-plastic film bag containing the slurry to a vacuum level of 0.01~0.02 MPa, and then sealing it; 5) measuring the volume of gas produced: fixing the sealed aluminum-plastic film bag to the bottom of a container, completely immersing it in the measuring medium, and recording the volume density of the aluminum-plastic film bag. After gas is produced, the volume density is recorded again. The shortcomings of this patent are: it is difficult to accurately evaluate the more microscopic gas production reaction, it cannot accurately determine whether there is a significant inhibitory effect on the gas production of the electrolyte, and it cannot determine whether the residual alkali content on the surface will affect the electrolyte. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a simple method that can accurately evaluate whether the coating of pre-lithiated silicon-oxygen anode material in lithium-ion batteries is complete and dense. This method can more accurately determine the inhibitory effect of pre-lithiated silicon-oxygen anode material on electrolyte penetration, and whether the content of residual alkaline substances on the surface will affect the electrolyte.

[0008] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0009] A method for inspecting the coating integrity of pre-lithiated silicon-oxygen anode material by immersion in electrolyte includes the following steps:

[0010] (1) Place the pre-lithiated silicon-oxygen anode material to be tested into the sample container and dry it together with the experimental instruments in a vacuum drying oven;

[0011] (2) After drying, take out all items and put them into the glove box transition chamber for ventilation. After ventilation, place all items in the glove box, drip the electrolyte into the pre-lithiated silicon oxygen anode material, stir well, and take out the sample container.

[0012] (3) Place the sample container in a vacuum drying oven and heat it under vacuum;

[0013] (4) Take out the sample container, filter and clean the sample, vacuum dry it, and then perform characterization tests. If the sample turns pale yellow after being soaked in the electrolyte, and the characterization tests show peaks of Li2SiF6 and LiF as well as the formation of an organic layer, it indicates that the pre-lithiated silicon-oxygen anode material to be tested is not fully coated. If there is no obvious color change before and after soaking in the electrolyte, and there is no obvious difference in the characterization tests before and after soaking, it indicates that the pre-lithiated silicon-oxygen anode material to be tested is fully and densely coated.

[0014] In the above method, preferably, in step (1), the pre-lithiated silicon-oxygen anode material to be tested is either an incompletely coated pre-lithiated silicon-oxygen anode material or a completely and densely coated pre-lithiated silicon-oxygen anode material.

[0015] Preferably, the sample container is a glass sample bottle, and the experimental instruments include a glass dropper and a glass rod.

[0016] Preferably, in steps (1) and (4), the drying temperature is 80℃~120℃ and the drying time is more than 4 hours. Vacuum drying mainly evaporates the moisture from the materials and experimental instruments, reducing the impact of moisture on the oxygen value of the glove box. In addition, moisture can cause the hydrolysis of lithium salts, producing undesirable byproducts. Drying the materials can avoid the impact of moisture on the electrolyte during the soaking process.

[0017] Preferably, in step (2), the sample container is kept tightly closed throughout the process of being taken out of the drying oven and transferred to the glove box transition chamber. All items are exposed to the air for no more than 2 minutes to prevent moisture from entering the air and to ensure that the sample container and experimental instruments remain dry.

[0018] Preferably, in step (2), the number of air exchanges is more than 3 times, the purpose of which is to remove the oxygen on the surface of the sample container and experimental instruments and reduce its impact on the oxidation of the electrolyte; after placing all items in the glove box, leave them for a period of time until the water oxygen value in the glove box is less than 0.01ppm, and then drip the electrolyte into the pre-lithiated silicon oxygen anode material for immersion.

[0019] Preferably, in step (2), the electrolyte comprises LiPF6, an ethylene carbonate-diethyl carbonate-dimethyl carbonate co-solvent, carbonate, and fluoroethylene carbonate, wherein the volume ratio of LiPF6, co-solvent, and carbonate is (1.5~2.2):(0.8~1.2):(1.5~2.2), and the mass of fluoroethylene carbonate is 7-12 wt% of the electrolyte. Adding the electrolyte after opening the sample container in a glove box for a period of time is mainly to reduce the water and oxygen value of the material through the circulation function of the glove box. Once the water and oxygen value in the glove box is less than 0.01 ppm, the electrolyte can be added. The electrolyte can be any commonly used in negative electrode materials.

[0020] Preferably, in step (3), the vacuum heating temperature is 60℃~100℃, and the vacuum heating time is 48h~72h. The temperature and time of vacuum drying should not be too high or too long. Too high a temperature and too long a time may cause the electrolyte to decompose and the carbon layer to react with the electrolyte, resulting in too many side reactions and affecting the judgment of the experimental results.

[0021] Preferably, in step (4), the solvent used for cleaning is carbonate. Carbonate can effectively dissolve a variety of organic and inorganic salts, making it suitable for cleaning the electrolyte on the surface of pre-lithiated silicon-oxygen anode materials. Compared with other solvents, carbonate has lower toxicity and less impact on the environment and human body, making it more in line with the requirements of green chemistry. Carbonate has moderate volatility and can evaporate quickly after cleaning, avoiding residual carbonate from affecting the judgment of subsequent test results. In addition, carbonate has good chemical stability and is not prone to side reactions, ensuring the cleaning effect on the electrolyte. Compared with other high-end solvents, carbonate has a relatively moderate cost and is suitable for large-scale applications.

[0022] Preferably, in step (4), the characterization test includes any one or more of XRD, TEM, and SEM.

[0023] Testing revealed that the incompletely coated pre-lithiated silicon-oxygen anode material exhibited a distinctly pale yellow hue in the electrolyte after immersion. The primary reason for this color change was the presence of residual Li₂CO₃ and LiOH on the surface, which caused electrolyte decomposition under heating conditions, leading to the color change. XRD analysis revealed the formation of significant Li₂SiF₆ and LiF peaks, while the intensity of the Li₂SiO₃ diffraction peak was significantly reduced. TEM and SEM characterization clearly showed the formation of a thick organic layer. The formation of Li₂SiF₆ is due to the incomplete carbon layer coating after pre-lithiation, allowing the electrolyte to easily penetrate and react with the silicon grains (Si + 2LiPF₆ → Li₂SiF₆ + 2PF₃), hence the obvious diffraction peaks observed in XRD. The formation of LiF and the thick organic layer is mainly due to the decomposition of LiPF₆ and other electrolyte components caused by alkaline substances, resulting in the growth of LiF and electrolyte decomposition products on the carbon layer surface, thus revealing the obvious LiF diffraction peaks and the thick organic layer. The modified pre-lithiated silicon anode oxygen material showed no obvious color change in the electrolyte, and there was no significant difference in the test characterization before and after immersion.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] This invention aims to accurately evaluate whether the coating of pre-lithiated silicon-oxygen anode materials is complete and dense. It provides a simple and accurate method for evaluating whether the coating of pre-lithiated silicon-oxygen anode materials in lithium-ion batteries is complete and dense. This method can more accurately determine the inhibitory effect of pre-lithiated silicon-oxygen anode materials on electrolyte penetration and whether the content of residual alkaline substances on the surface will affect the electrolyte. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 The figure shows the experimental results of the observation of gas generation phenomenon of (a) unmodified and (b) modified pre-lithiated silicon-oxygen.

[0028] Figure 2 The figures show the experimental results of heating and soaking the unmodified, modified, and blank control electrolytes in Example 1 of this invention.

[0029] Figure 3 The images shown are XRD patterns of unmodified pre-lithiated silicon oxide before and after immersion in Example 1 of the present invention.

[0030] Figure 4 This is a transmission electron microscope (TEM) image of the surface morphology of unmodified pre-lithiated silicon oxide after immersion in Example 1 of the present invention.

[0031] Figure 5 This is a scanning electron microscope image of the surface morphology of unmodified pre-lithiated silicon oxide after immersion in Example 1 of the present invention;

[0032] Figure 6 The images shown are XRD patterns of the modified pre-lithiated silicon oxide before and after immersion in the substrate in Example 1 of this invention.

[0033] Figure 7 This is a transmission electron microscope (TEM) image of the surface morphology of the modified pre-lithiated silicon oxide after immersion in Example 1 of the present invention.

[0034] Figure 8 This is a scanning electron microscope image of the surface morphology of the modified pre-lithiated silicon oxide after immersion in Example 1 of the present invention;

[0035] Figure 9 The figures show the experimental results of the electrolytes of unmodified 2 and blank control 2 after heating and soaking in the present invention.

[0036] Figure 10 The image shown is the XRD pattern of the unmodified pre-lithiated silicon oxide after immersion in the silicon oxide in Example 2 of this invention.

[0037] Figure 11 The images are scanning electron microscope (SEM) images of the surface morphology of the unmodified pre-lithiated silicon oxide 2 before (a) immersion and after (b) immersion in the pre-lithiated silicon oxide 2 of Example 2 of the present invention.

[0038] Figure 12 The figures show the experimental results of the electrolyte of unmodified 3 and blank control 3 after heating and soaking in the present invention.

[0039] Figure 13 The image shown is the XRD pattern of the unmodified pre-lithiated silicon oxide after immersion in Example 3 of the present invention.

[0040] Figure 14 The images are scanning electron microscope (SEM) images of the surface morphology of the unmodified pre-lithiated silicon oxide 3 before (a) immersion and after (b) immersion in the 3rd embodiment of the present invention.

[0041] Figure 15 The figures show the experimental results of the modified electrolyte 2 and blank control 4 after heating and soaking in the electrolyte of Example 4 of the present invention.

[0042] Figure 16 The image shown is the XRD pattern of the modified 2 pre-lithiated silicon oxide after immersion in the substrate in Example 5 of this invention.

[0043] Figure 17 The images are scanning electron microscope (SEM) images of the surface morphology of the modified 2 pre-lithiated silicon oxide before (a) and after (b) immersion in the immersion solution in Example 6 of the present invention. Detailed Implementation

[0044] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0045] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0046] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0047] The following examples use unmodified pre-lithiated silicon-oxygen anode material to simulate incompletely coated pre-lithiated silicon-oxygen anode material, and modified pre-lithiated silicon-oxygen anode material to simulate fully coated and densely coated pre-lithiated silicon-oxygen anode material. The unmodified pre-lithiated silicon-oxygen anode material is obtained by mixing and sintering ordinary carbon-coated silicon-oxygen anode material with a lithium source without any post-processing. The modified pre-lithiated silicon-oxygen anode material is obtained by secondary carbon coating and surface modification of the pre-lithiated silicon-oxygen anode material through chemical vapor deposition. It has low residual alkali content and complete and dense coating. The specific preparation method is as follows:

[0048] CMC (carboxymethyl cellulose) (solid content 1.12%), SP (carbon black), the sample (pre-lithiated silica material before and after modification), graphite, and SBR (styrene-butadiene rubber) (solid content 40%) were added sequentially to a mixing cup and stirred using a vacuum degassing mixer. After stirring, 10g of the slurry was weighed, placed in a vacuum-sealed bag, and vacuum-sealed using a sealing machine. Finally, the vacuum-sealed bag was placed in a constant temperature environment of 25℃ to observe the gas generation phenomenon. The comparison of the gas generation evaluation experimental results of the unmodified and modified pre-lithiated silica materials is shown in Table 1. Figure 1 .

[0049] Table 1: Gas generation evaluation experiments of unmodified and modified pre-lithiated silicon-oxygen anode materials

[0050]

[0051] From Table 1, Figure 1 It can be seen that the unmodified pre-lithiated silicon-oxygen anode material can be used to simulate the incompletely coated pre-lithiated silicon-oxygen anode material in the following embodiments, while the modified pre-lithiated silicon-oxygen anode material can be used to simulate the fully coated and dense pre-lithiated silicon-oxygen anode material in the following embodiments.

[0052] Example 1:

[0053] A method for inspecting the coating integrity of pre-lithiated silicon-oxygen anode material by immersion in electrolyte includes the following steps:

[0054] (1) Prepare the aforementioned unmodified and modified pre-lithiated silicon-oxygen anode materials and experimental instruments such as glass droppers and glass rods;

[0055] (2) Weigh 2g of each of the two materials and put them into a glass sample bottle. Then put the experimental instruments (glass dropper and glass rod) into a vacuum drying oven and dry them at 80℃ for more than 4 hours.

[0056] (3) Take out all items, quickly tighten the cap of the glass sample bottle, and then quickly put it into the glove box transition chamber for at least three ventilations; in the glove box, open the glass sample bottle and leave it for a period of time until the water and oxygen values ​​in the glove box are less than 0.01 ppm; then drop the electrolyte into the glass sample bottle, stir it with a glass rod until it becomes a mud-like state, tighten the cap, and take out the glass sample bottle; the specific components of the electrolyte include: 1M LiPF6, ethylene carbonate (EC)-diethyl carbonate (DEC)-dimethyl ester co-solvent, carbonate (volume ratio: LiPF6:cosolvent:carbonate = 2:1:2) and fluoroethylene carbonate (FEC) (accounting for 10 wt% of the entire electrolyte);

[0057] (4) Place the glass sample vials in a vacuum drying oven and heat them under vacuum at 60°C for 48 hours;

[0058] (5) Remove the sample vial, filter it first, and then wash it three times with carbonate. Dry it under vacuum at 80℃ for more than 4 hours, and then take out the sample for characterization tests such as XRD, TEM, and SEM. The electrolyte of the unmodified pre-lithiated silicon-oxygen anode material after soaking is obviously pale yellow, and XRD can observe obvious peaks of Li2SiF6 and LiF. TEM and SEM tests can clearly observe the formation of a thick organic layer. The electrolyte of the fully coated pre-lithiated silicon-oxygen anode material does not show obvious color change, and there is no obvious difference in the characterization before and after soaking. The XRD, SEM, and TEM characterization of the pre-lithiated silicon-oxygen anode material after secondary coating is not obviously different before and after soaking.

[0059] The experimental comparison of unmodified, modified, and blank control electrolytes after heating and soaking is shown in Tables 2-4. Figures 2-8 .

[0060] Table 2: Pre-lithiated silicon-oxygen anode materials (unmodified)

[0061]

[0062] Table 3: Pre-lithiated silicon-oxygen anode materials (after modification)

[0063]

[0064] Table 4: Blank Control

[0065]

[0066] From Tables 2-4, Figures 2-8 It can be seen that, compared with the unmodified material, the modified material showed no significant color change after immersion in the electrolyte, the XRD test results were not significantly different from those before immersion, and TEM and SEM tests showed no obvious organic layer. The blank control showed no significant color change after immersion in the electrolyte compared with the unmodified material, indicating that under the heating conditions of this temperature and time, no decomposition of the electrolyte would occur. This method can more accurately determine the inhibitory effect of the pre-lithiated silicon-oxygen anode material on electrolyte penetration, and whether the content of residual alkaline substances on the surface will affect the electrolyte.

[0067] Example 2:

[0068] A method for inspecting the coating integrity of pre-lithiated silicon-oxygen anode material by immersion in electrolyte includes the following steps:

[0069] (1) Prepare pre-lithiated silicon-oxygen anode material (unmodified 2) and experimental instruments such as glass dropper and glass rod;

[0070] (2) Weigh 2g of each of the two materials and put them into a glass sample bottle. Then put the experimental instruments (glass dropper and glass rod) into a vacuum drying oven and dry them at 80℃ for more than 4 hours.

[0071] (3) Take out all items, quickly tighten the cap of the glass sample bottle, and then quickly put it into the glove box transition chamber for at least three ventilations; in the glove box, open the glass sample bottle and leave it for a period of time until the water and oxygen values ​​in the glove box are less than 0.01 ppm; then drop the electrolyte into the glass sample bottle, stir it with a glass rod until it becomes a mud-like state, tighten the cap, and take out the glass sample bottle; the specific components of the electrolyte include: 1M LiPF6, ethylene carbonate (EC)-diethyl carbonate (DEC)-dimethyl ester co-solvent, carbonate (volume ratio: LiPF6:cosolvent:carbonate = 2:1:2) and fluoroethylene carbonate (FEC) (accounting for 10 wt% of the entire electrolyte);

[0072] (4) Place the glass sample vials in a vacuum drying oven and heat them under vacuum at 40°C for 24 hours;

[0073] (5) Take out the sample bottle, filter it first, and then wash it three times with carbonate. Dry it under vacuum at 80°C for more than 4 hours, and then take out the sample for characterization tests such as XRD, TEM, and SEM.

[0074] Table 5: Pre-lithiated silicon-oxygen anode materials (unmodified 2)

[0075]

[0076] Table 6: Blank Control 2

[0077]

[0078] From Tables 5-6, Figures 9-11 It can be seen that lowering the heating temperature and reducing the heating time can significantly slow down the decomposition and deposition of the electrolyte.

[0079] Example 3:

[0080] A method for inspecting the coating integrity of pre-lithiated silicon-oxygen anode material by immersion in electrolyte includes the following steps:

[0081] (1) Prepare pre-lithiated silicon-oxygen anode material (unmodified 3) and experimental instruments such as glass dropper and glass rod;

[0082] (2) Weigh 3g of each of the two materials and put them into a glass sample bottle. Then put the experimental instruments (glass dropper and glass rod) into a vacuum drying oven and dry them at 80℃ for more than 4 hours.

[0083] (3) Take out all items, quickly tighten the cap of the glass sample bottle, and then quickly put it into the glove box transition chamber for at least three ventilations; in the glove box, open the glass sample bottle and leave it for a period of time until the water and oxygen values ​​in the glove box are less than 0.01 ppm; then drop the electrolyte into the glass sample bottle, stir it with a glass rod until it becomes a mud-like state, tighten the cap, and take out the glass sample bottle; the specific components of the electrolyte include: 1M LiPF6, ethylene carbonate (EC)-diethyl carbonate (DEC)-dimethyl ester co-solvent, carbonate (volume ratio: LiPF6:cosolvent:carbonate = 2:1:2) and fluoroethylene carbonate (FEC) (accounting for 10 wt% of the entire electrolyte);

[0084] (4) Place the glass sample vials in a vacuum drying oven and heat them under vacuum at 60°C for 72 hours;

[0085] (5) Take out the sample bottle, filter it first, and then wash it three times with carbonate. Dry it in vacuum at 80°C for more than 4 hours, and then take out the sample for characterization tests such as XRD, TEM, and SEM.

[0086] Table 7: Pre-lithiated silicon-oxygen anode materials (unmodified 3)

[0087]

[0088] Table 8: Blank Control 3

[0089]

[0090] From Tables 7-8, Figures 12-14 It can be seen that extending the heating time and increasing the mass of the soaked material can significantly accelerate the decomposition and deposition of the electrolyte.

[0091] Example 4:

[0092] A method for inspecting the coating integrity of pre-lithiated silicon-oxygen anode material by immersion in electrolyte includes the following steps:

[0093] (1) Prepare pre-lithiated silicon-oxygen anode material (modified 2) and experimental instruments such as glass dropper and glass rod;

[0094] (2) Weigh 2g of each of the two materials and put them into a glass sample bottle. Then put the experimental instruments (glass dropper and glass rod) into a vacuum drying oven and dry them at 80℃ for more than 4 hours.

[0095] (3) Take out all items, quickly tighten the cap of the glass sample bottle, and then quickly put it into the glove box transition chamber for at least three ventilations; in the glove box, open the glass sample bottle and leave it for a period of time until the water and oxygen values ​​in the glove box are less than 0.01 ppm; then drop the electrolyte into the glass sample bottle, stir it with a glass rod until it becomes a mud-like state, tighten the cap, and take out the glass sample bottle; the specific components of the electrolyte include: the main component is 1M LiPF6, and the co-solvent of ethylene carbonate (EC)-diethyl carbonate (DEC)-dimethyl ester, carbonate (volume ratio = 2:1:2) and 10 wt% fluoroethylene carbonate (FEC), etc.

[0096] (4) Place the glass sample vials in a vacuum drying oven and heat them under vacuum at 70°C for 72 hours;

[0097] (5) Take out the sample bottle, filter it first, and then wash it three times with carbonate. Dry it in vacuum at 80°C for more than 4 hours, and then take out the sample for characterization tests such as XRD, TEM, and SEM.

[0098] Table 9: Pre-lithiated silicon-oxygen anode materials (Modified 2)

[0099]

[0100] Table 10: Blank Control 4

[0101]

[0102] From Tables 9-10, Figures 15-17It can be seen that for fully and densely coated pre-lithiated silicon oxide materials, even if the heating temperature is increased and the heating time is extended within the above-mentioned conditions, it is impossible to promote the side reactions of the electrolyte.

[0103] In summary, the method of the present invention can more accurately determine the inhibitory effect of pre-lithiated silicon-oxygen anode material on electrolyte penetration, and whether the content of residual alkaline substances on the surface will affect the electrolyte.

Claims

1. A method for testing the integrity of a prelithiated silicon-oxygen anode material by electrolyte immersion, characterized in that, The method comprises the following steps: (1) placing the pre-lithiated silicon-oxygen negative electrode material to be tested into a sample container, and placing the sample container and experimental instruments into a vacuum drying box for drying; (2) after drying, taking out all the articles and placing them into a glove box transition cabin for air exchange, and after air exchange, placing all the articles in the internal space of the glove box, dropping electrolyte into the pre-lithiated silicon-oxygen negative electrode material for soaking, stirring, and taking out the sample container; the electrolyte comprises LiPF6, ethylene carbonate-diethyl carbonate-dimethyl carbonate cosolvent, carbonate, and fluoroethylene carbonate, wherein the volume ratio of LiPF6, the cosolvent, and the carbonate is (1.5-2.2):(0.8-1.2):(1.5-2.2), and the mass of the fluoroethylene carbonate is 7-12 wt% of the electrolyte; (3) placing the sample container into the vacuum drying box for vacuum heating; (4) taking out the sample container, cleaning the sample after suction filtration, vacuum drying, and then performing characterization testing; if the electrolyte presents a light yellow color after soaking, and the characterization testing finds that Li2SiF6, LiF peaks and an organic layer are generated, it is indicated that the pre-lithiated silicon-oxygen negative electrode material to be tested is incompletely coated; if there is no obvious color change before and after soaking, and the test characterization before and after soaking has no obvious difference, it is indicated that the pre-lithiated silicon-oxygen negative electrode material to be tested is completely and densely coated.

2. The method of claim 1, wherein, In step (1), the pre-lithiated silicon-oxygen negative electrode material to be tested is a pre-lithiated silicon-oxygen negative electrode material incompletely coated or a pre-lithiated silicon-oxygen negative electrode material completely and densely coated.

3. The method of claim 1, wherein, In step (1), the sample container is a glass sample bottle, and the experimental instruments comprise a glass rubber head dropper and a glass rod.

4. The method of claim 1, wherein, In steps (1) and (4), the drying temperature is 80-120 DEG C, and the drying time is more than 4 h.

5. The method of claim 1, wherein, In step (2), the sample container is in a tightly covered state during the whole process from being taken out of the drying box to the glove box transition cabin, and the exposure time of all the articles in the air is not more than 2 min.

6. The method of claim 1, wherein, In step (2), the air exchange is performed more than 3 times; after placing all the articles in the internal space of the glove box, the articles are placed for a period of time until the water and oxygen values in the glove box are less than 0.01 ppm, and then the electrolyte is dropped into the pre-lithiated silicon-oxygen negative electrode material for soaking.

7. The method of claim 1, wherein, In step (3), the vacuum heating temperature is 60-100 DEG C, and the vacuum heating time is 48-72 h.

8. The method of claim 1, wherein, In step (4), the solvent used for cleaning is carbonate.

9. The method of claim 1, wherein, In step (4), the characterization testing comprises any one or more of XRD, TEM, and SEM.

Images