A battery negative electrode composition and preparation method thereof

Abstract

The present application relates to the technical field of lithium-ion battery negative electrode materials, and specifically discloses a battery negative electrode composition and a preparation method thereof. The battery negative electrode composition is made of the following raw materials in parts by mass: 150-180 parts of N-methylpyrrolidone, 75-90 parts of an organic modified component, 3-5 parts of a binder, 3-5 parts of a thickener, and 1-2 parts of carbon black. The preparation of the organic modified component includes: (S01) nano-alumina crushing treatment, (S02) organic modification of crushed nano-alumina, (S03) graphite edge oxidation treatment, and (S04) preparation of a composite material. The organic modified component prepared in the present application has the advantages of stabilizing the SEI film and reducing the risk of lithium dendrite generation in lithium-ion batteries.

Description

Technical Field

[0001] The present application relates to the technical field of lithium-ion battery negative electrode materials, and more specifically, to a battery negative electrode composition and a preparation method thereof. Background Art

[0002] Lithium-ion batteries, also known as lithium secondary batteries, are batteries that charge and discharge via the movement of lithium ions between positive and negative electrodes. In recent years, the global lithium-ion battery market has continued to expand. Demand for lithium-ion batteries has continued to grow, driven in particular by the rapid development of new energy vehicles, energy storage systems, and consumer electronics.

[0003] A complete non-solid-state lithium-ion battery is mainly composed of a positive electrode, a negative electrode, an electrolyte, a separator, and a casing. Among them, the positive and negative electrodes are key components of lithium-ion batteries and play a vital role in the charge and discharge performance of lithium-ion batteries. The positive electrode of the battery is mainly made by coating a lithium-containing compound slurry on an aluminum foil current collector and then undergoing heat treatment or drying; while the negative electrode of the battery is mainly made by coating a graphite-based slurry on a copper current collector and then undergoing heat treatment or drying. Since the negative electrode of the battery is mainly responsible for releasing charge during the discharge process in a lithium-ion battery, the properties of the negative electrode of the battery directly affect the discharge efficiency of the lithium-ion battery and have an impact on the battery's discharge capacity.

[0004] Lithium-ion battery anodes made with graphite-based slurries undergo electrolyte decomposition during the initial charge and discharge cycles. This decomposed electrolyte forms a SEI film at the edges of the graphite coated on the copper current collector. Currently, most lithium-ion batteries use LiPF6 as the conductive salt, resulting in a uniform SEI film. This SEI film is an excellent conductor of lithium ions, hindering further electrolyte decomposition and promoting lithium ion circulation, thereby improving the battery's cycle life. However, this SEI film is not stable. The LiPF6 component, in particular, is easily decomposed by environmental factors and reacts with the small amount of water present in the lithium-ion battery, damaging the SEI film and forming defects. Simultaneously, new SEI films grow from these defects. Due to environmental disturbances, the re-formed SEI film is uneven and can easily induce lithium dendrites, leading to a decrease in battery electrochemical performance. Therefore, stabilizing the SEI film and mitigating the dendrite problem in lithium-ion batteries is crucial for their long-term performance.

[0005] Chinese patent application publication number CN111416120A discloses a lithium metal material with an artificially constructed polymer SEI membrane, as well as its preparation and application. Using commercial Kevlar fibers as a raw material, a pure Kevlar nanofiber dispersion is prepared and coated onto a lithium substrate. This artificial SEI membrane replaces the SEI naturally formed in the electrolyte of the lithium-ion battery's negative electrode, resulting in an artificial SEI membrane. The assembled SEI membrane exhibits high strength and flexibility, stabilizing the SEI and inhibiting the growth of lithium dendrites.

[0006] While the aforementioned document achieves an artificial SEI membrane through assembly, avoiding many of the drawbacks of a battery's naturally occurring SEI membrane, the high price of the Kevlar nanofibers used in the application increases the cost of industrial production. Furthermore, the replacement of a naturally occurring SEI membrane with an artificial assembly increases the production cycle and difficulty of lithium-ion batteries. Therefore, the need remains to find a cost-effective way to stabilize the SEI membrane and extend the life of lithium-ion batteries. Summary of the Invention

[0007] In order to further obtain a method for stabilizing the SEI film and reducing the lithium dendrite problem of lithium-ion batteries, the present application provides a battery negative electrode composition and a preparation method thereof.

[0008] In a first aspect, the present application provides a battery negative electrode composition, which is made from the following raw materials in parts by mass: 150-180 parts of N-methylpyrrolidone, 75-90 parts of an organic modification component, 3-5 parts of a binder, 3-5 parts of a thickener, and 1-2 parts of carbon black;

[0009] The organic modified component is prepared by the following steps:

[0010] (S01) mixing nano-alumina, water, and abrasive, subjecting the mixture to ultrasonic crushing, filtering impurities, and drying to obtain crushed nano-alumina;

[0011] (S02) dissolving and dispersing the crushed nano-alumina, stirring for the first time, adding choline chloride, adjusting the pH and temperature, stirring for the second time, and removing the solvent and drying the treated product to obtain organically modified nano-alumina;

[0012] (S03) adding graphite to abrasive, grinding, washing and filtering, taking the precipitate and adding it to concentrated sulfuric acid for acid leaching, adding NaNO3, controlling the initial reaction temperature, stirring, then adding potassium permanganate to the system, heating, diluting with water, and finally adding hydrogen peroxide solution, the product is centrifuged, the precipitate is washed and dried to obtain edge carboxyl graphite oxide;

[0013] (S04) mixing and dissolving the organically modified nano-alumina and the edge carboxyl graphite oxide, adding a dispersant and a catalyst, and heating the mixture to obtain an organically modified component.

[0014] By adopting the above technical solution, an organically modified component with a stable negative electrode SEI film can be obtained. During the initial charge and discharge of a battery, the SEI film tends to grow at the edges of the graphite due to the coating state of the graphite-based slurry and the layered structure of the graphite itself. Therefore, modifying the graphite edges is one of the most effective ways to improve SEI stability. The organically modified component is obtained by oxidizing the carboxyl groups at the graphite edges and combining them with an organically modified nano-alumina through an esterification reaction. When water molecules in the battery approach the negative electrode SEI film, the nano-alumina absorbs the water molecules through hydrogen bonds and vacancy defects. The choline chloride in the organically modified nano-alumina acts as a Lewis base to capture PF5 generated by the decomposition of LiPF6 in the SEI component, isolating it from the SEI film and preventing further decomposition of PF5 on the SEI film, which could produce HF that corrodes the SEI film. The combined effects of the organically modified component enhance the stability of the SEI film formed at the negative electrode.

[0015] Preferably, in the step (S01), the abrasive is 60-mesh corundum.

[0016] By adopting the above technical solution, nano-alumina can be further broken down. The Mohs hardness of nano-alumina is 9, while the Mohs hardness of corundum is 9.5. Through ultrasonic crushing treatment, nano-alumina and corundum collide continuously and violently, and the nano-alumina with lower hardness is broken into small pieces due to the collision, and the nano size is further reduced, thereby obtaining nano-alumina with smaller particle size. The broken nano-alumina is conducive to the subsequent grafting with graphite oxidized by edge carboxyl groups and the preparation of a smoother slurry. At the same time, the internal hydroxyl binding sites of the broken nano-alumina are fully exposed, which can form more hydrogen bonds, and the structure of the organic modified component prepared by subsequent treatment is more stable.

[0017] Preferably, in the step (S01), the ultrasonic crushing treatment time is 2-3 hours.

[0018] By adopting the above technical solution, when the processing time is set to 2-3h, the nano-alumina crushing effect is best.

[0019] Preferably, in the step (S02), the first stirring speed is 200-350 rpm, and the second stirring speed is 50-75 rpm; the pH is adjusted to 6-6.5 and the temperature is 35-40°C.

[0020] By adopting the above technical solution, a higher stirring speed is set during the first magnetic stirring, which can make the nano-alumina more evenly dispersed. If the second stirring is controlled at a low speed, it can promote a more effective grafting effect between choline chloride and nano-alumina. There are many vacancy defects on the surface of nano-alumina, which can provide active sites for adsorption of polar choline chloride molecules. After being crushed, the nano-alumina has an increased specific surface area, which produces more sites that can adsorb choline chloride. At the same time, choline chloride can form hydrogen bonds with the hydroxyl groups on the surface of nano-alumina, strengthening the combination of choline chloride and nano-alumina. This combination effect is best when the system pH is 6-6.5 and the temperature is 35-40°C.

[0021] Preferably, in the step (S03), the abrasive is sodium chloride with a particle size ≥1 mm.

[0022] By adopting the above technical solution, the addition of sodium chloride can help disperse, remove impurities and improve the purity of graphite. At the same time, the finer graphite powder obtained by grinding is conducive to enhancing the dispersibility and fluidity of the subsequent graphite in the composite solution.

[0023] Preferably, in the step (S03), the initial reaction temperature is set to (-5)-(-2)°C, and the stirring is performed for 20-30 minutes; and the mass concentration of the hydrogen peroxide solution is 25%-30%.

[0024] By adopting the above technical solution and controlling the initial reaction temperature and time, the weak oxidation process of graphite can be regulated to obtain a graphite structure with oxidized edge carboxyl groups. Graphite oxidation is a gradual process, and the degree of oxidation increases with increasing system temperature and reaction time. When the oxidizing environment is relatively weak, oxidation is concentrated at the edges of the graphite layers; when oxidation is intense, the distance between the graphite layers is opened, and oxidation can occur simultaneously at the layers and edges. However, intense oxidation of graphite is detrimental to the preparation of battery negative electrode compositions, so it is necessary to control the temperature and time as described above to weakly oxidize the edges of the graphite to insert carboxyl groups.

[0025] Preferably, in the step (S04), the mass ratio of the organically modified nano-alumina to the edge carboxyl graphite oxide is 1:(1.5-3.5).

[0026] By adopting the above technical solution, when preparing a battery negative electrode composition, when the mass ratio of organically modified nano-alumina to edge carboxyl graphite oxide is 1:(1.5-3.5), the obtained organically modified component has the best use effect.

[0027] Preferably, in the step (S04), the dispersant is one of sodium lauryl sulfate, sodium tripolyphosphate, polyvinyl alcohol, and polyethylene glycol.

[0028] Preferably, in the step (S04), the catalyst is p-toluenesulfonic acid; and the temperature treatment operation is: heating the temperature to 75-85° C., magnetic stirring speed 100-150 rpm, and continuing for 2.5-4 hours.

[0029] By adopting the above technical solution, a complete graft structure can be obtained. p-Toluenesulfonic acid, a non-oxidizing esterification catalyst, can avoid the oxidative decomposition of choline chloride grafted onto the nano-alumina when using an oxidizing esterification catalyst, thereby ensuring the integrity of the graft structure. By regulating the temperature treatment operation, the optimal grafting effect can be achieved.

[0030] In a second aspect, the present application provides a method for preparing a battery negative electrode composition, comprising the following steps:

[0031] The organic modified component, N-methylpyrrolidone, a binder, carbon black and a thickener are mixed and stirred uniformly to obtain a battery negative electrode composition.

[0032] In summary, this application has the following beneficial effects:

[0033] 1. This application prepares an organically modified component by crushing nano-alumina, organically modifying the crushed nano-alumina, oxidizing the graphite edges, and preparing a composite material. A battery negative electrode composition made from this composite material, when used in a lithium-ion battery, forms a stable SEI membrane structure after the initial charge and discharge, reducing the occurrence of lithium dendrites within the battery material.

[0034] 2. For non-solid-state lithium-ion batteries using LiPF6 as a conductive salt, during the first charge and discharge, the LiPF6 component in the formed SEI film will undergo a spontaneous decomposition reaction: The generated PF5 will react with a small amount of water molecules in the electrolyte environment and produce a chain reaction. The reaction can be expressed as: , , producing acidic substances that can corrode the negative electrode of the battery. The loss of SEI components and the corrosion of acidic substances will eventually destroy the SEI layer structure. The prepared organic modified components have a comprehensive effect. On the one hand, for the SEI film grown on the edge of graphite, the grafted nano-alumina can capture water molecules through surface hydroxyl groups and vacancy defects, thereby inhibiting the continued decomposition of PF5. On the other hand, the nano-alumina is modified with choline chloride, and choline chloride molecules exist on the surface. The PF5 generated during the decomposition reaction of LiPF6 is a Lewis acid, which can be captured by the Lewis base choline chloride, thereby inhibiting the HF generated by the continued decomposition of PF5 from corroding the SEI film. Through the combined effect, a stable SEI film is finally obtained at the negative electrode of the lithium-ion battery.

[0035] 3. The battery negative electrode prepared using the battery negative electrode composition prepared in this application has an initial coulombic cycle efficiency of ≥92.428% after assembly, and a capacity retention rate of more than 90% after 500 cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The gas volume and titration test results of the soft-package lithium-ion batteries of Examples 1-5 and Comparative Examples 1-2 of the present application were tested by powering on. DETAILED DESCRIPTION

[0037] Example 1

[0038] A battery negative electrode composition is prepared from the following raw materials in parts by mass: 85 parts of an organic modification component, 150 parts of N-methylpyrrolidone, 3 parts of a binder of polyvinylidene fluoride, 1 part of carbon black, and 3 parts of a thickener of sodium carboxymethyl cellulose.

[0039] The preparation steps of the organic modified component in this embodiment are as follows:

[0040] (S01) 8 g of nano-alumina, 20 mL of deionized water, and 3 g of corundum were mixed and crushed using a BILON-150Y ultrasonic cell crusher. The temperature was set to 65°C, the horn diameter was 6 mm, and the ultrasonic mode was set to 2 seconds with 2 seconds intervals. The treatment was continued for 2 hours. The sonicated product was then dehydrated, filtered to remove the contaminated corundum, and dried to obtain the crushed nano-alumina.

[0041] (S02) 7.5 g of crushed nano-alumina was dissolved in 40 mL of anhydrous ethanol solvent, 0.3 g of dispersant polyethylene glycol was added to the system for dispersion treatment, the initial stirring speed was controlled at 200 rpm, and then 0.5 g of choline chloride was added to the mixed system, the pH of the system was adjusted to 6, and then the magnetic stirring speed was reduced by 50 rpm, the system temperature was controlled at 35°C, and stirred for 1 hour. The product was desolventized and dried to obtain organically modified nano-alumina.

[0042] (S03) 4 g of graphite was ground with sodium chloride (1 mm), then washed and filtered to remove the sodium chloride. The dried graphite was immersed in 60 mL of 98% concentrated sulfuric acid, followed by the addition of 0.3 g of NaNO3. The initial reaction temperature was controlled at -5°C, and the magnetic stirring speed was 150 rpm. After 20 min of reaction, 2.1 g of potassium permanganate was slowly added to the system. The system temperature was controlled and slowly increased at a rate of 2°C / min until it reached 30°C. The reaction was continued for 20 min. Deionized water was then added to the reaction system in multiple portions. During the first 50 mL of deionized water, the addition rate was controlled at 5 mL / min, and the magnetic stirring speed was controlled at 150 rpm. A total of 300 mL of deionized water was added to the solution to continuously dilute the concentration of concentrated sulfuric acid. Finally, 20 mL of 25% hydrogen peroxide solution was added to the system to stabilize the product. The reaction was terminated by stirring for another 6 h. The product was centrifuged, washed, and dried to obtain edge-carboxylated graphite oxide.

[0043] (S04) 3.3 g of the prepared organically modified nano-alumina was mixed with 5.7 g of graphite with edge carboxyl oxidation, dissolved in 45 mL of anhydrous ethanol, 0.2 g of dispersant polyethylene glycol and 1 g of p-toluenesulfonic acid were added, the system temperature was controlled at 75 ° C, the magnetic stirring speed was 100 rpm, and stirred for 2.5 hours to obtain an organically modified component.

[0044] The preparation steps of the battery negative electrode composition in this embodiment are as follows: 0.85g of an organic modified component, 1.5g of N-methylpyrrolidone, 0.03g of a binder, 0.01g of carbon black, and 0.03g of a thickener, sodium carboxymethyl cellulose, are mixed and stirred uniformly to obtain a battery negative electrode composition.

[0045] Among them, nano-alumina (model: MG-Al2O3-10, average particle size 10nm, pore volume 0.42-0.45cm 3 / g, specific surface area 160m 2 / g) was provided by Shanghai Maoguo Nanotechnology Co., Ltd. Diamond (60 mesh) was provided by Jiyuan Xingrui Sand Factory. Choline chloride (content 98%, pH 6.5) was provided by Shandong Fengtai Biotechnology Co., Ltd. Graphite (solid carbon content ≥80%, density 1.2g / cm 3 ) was provided by Ningbo Ding Innovation Materials Co., Ltd. Polyvinylidene fluoride (model: JX202) was provided by Nanjing Zengyun Nanomaterials Co., Ltd.

[0046] Example 2

[0047] A battery negative electrode composition is prepared from the following raw materials in parts by mass: 90 parts of an organic modification component, 150 parts of N-methylpyrrolidone, 4 parts of a binder of polyvinylidene fluoride, 2 parts of carbon black, and 3 parts of a thickener of sodium carboxymethyl cellulose.

[0048] The preparation steps of the organic modified component in this embodiment are as follows:

[0049] (S01) 8 g of nano-alumina, 20 mL of deionized water, and 3 g of corundum were mixed and crushed using a BILON-150Y ultrasonic cell crusher. The temperature was set to 65°C, the horn diameter was 6 mm, and the ultrasonic mode was set to 2 seconds with 2 seconds intervals, for 2.5 hours. The sonicated product was then dehydrated, filtered to remove the contaminated corundum, and dried to obtain the crushed nano-alumina.

[0050] (S02) 7.5 g of crushed nano-alumina was dissolved in 40 mL of anhydrous ethanol solvent, 0.3 g of polyethylene glycol was added to the system for dispersion treatment, the initial stirring speed was controlled at 250 rpm, and then 0.5 g of choline chloride was added to the mixed system, the pH of the system was adjusted to 6.5, and then the magnetic stirring speed was reduced to 75 rpm, the system temperature was controlled at 40 ° C, and stirred for 1.5 hours. The product was desolventized and dried to obtain organically modified nano-alumina.

[0051] (S03) 4 g of graphite was ground with sodium chloride (2.5 mm), then washed and filtered to remove the sodium chloride. The dried graphite was immersed in 60 mL of 98% concentrated sulfuric acid, followed by the addition of 0.3 g of NaNO3. The initial reaction temperature was maintained at -5°C with a magnetic stirring speed of 150 rpm. After 25 min of reaction, 2.1 g of potassium permanganate was slowly added to the system. The system temperature was controlled and slowly increased at a rate of 2°C / min until it reached 30°C. The reaction was continued for 20 min. Deionized water was then added to the reaction system in multiple portions. During the first 50 mL of deionized water, the addition rate was controlled at 5 mL / min and the magnetic stirring speed was controlled at 150 rpm. A total of 300 mL of deionized water was added to the solution to continuously dilute the concentration of concentrated sulfuric acid. Finally, 20 mL of 25% hydrogen peroxide solution was added to stabilize the product. The reaction was terminated by stirring for another 6 h. The product was centrifuged, washed, and dried to obtain edge-carboxylated graphite oxide.

[0052] (S04) 3 g of the prepared organically modified nano-alumina was mixed with 6 g of edge carboxyl graphite oxide, dissolved in 45 mL of anhydrous ethanol, 0.2 g of dispersant polyethylene glycol and 1 g of p-toluenesulfonic acid were added, the system temperature was controlled at 80 ° C, the magnetic stirring speed was 100 rpm, and stirred for 3 h to obtain an organically modified component.

[0053] The preparation steps of the battery negative electrode composition in this embodiment are as follows: 0.9 g of an organic modified component, 1.5 g of N-methylpyrrolidone, 0.04 g of a binder, 0.02 g of carbon black, and 0.03 g of a thickener, sodium carboxymethyl cellulose, are mixed and stirred uniformly to obtain a battery negative electrode composition.

[0054] Among them, nano-alumina (model: MG-Al2O3-10, average particle size 10nm, pore volume 0.42-0.45cm 3 / g, specific surface area 160m 2 / g) was provided by Shanghai Maoguo Nanotechnology Co., Ltd. Diamond (60 mesh) was provided by Jiyuan Xingrui Sand Factory. Choline chloride (content 98%, pH 6.5) was provided by Shandong Fengtai Biotechnology Co., Ltd. Graphite (solid carbon content ≥80%, density 1.2g / cm 3 ) was provided by Ningbo Ding Innovation Materials Co., Ltd. Polyvinylidene fluoride (PVDF) (Model: JX202) was provided by Nanjing Zengyun Nanomaterials Co., Ltd.

[0055] Example 3

[0056] A battery negative electrode composition is prepared from the following raw materials in parts by mass: 90 parts of an organic modification component, 160 parts of N-methylpyrrolidone, 5 parts of a binder of polyvinylidene fluoride, 2 parts of carbon black, and 5 parts of a thickener of sodium carboxymethyl cellulose.

[0057] The preparation steps of the organic modified component in this embodiment are as follows:

[0058] (S01) 8 g of nano-alumina, 20 mL of deionized water, and 3 g of corundum were mixed and crushed using a BILON-150Y ultrasonic cell crusher. The temperature was set to 65°C, the horn diameter was 6 mm, and the ultrasonic mode was set to 2 seconds with 2 seconds intervals. The treatment was continued for 3 hours. The sonicated product was then dehydrated, filtered to remove the contaminated corundum, and dried to obtain the crushed nano-alumina.

[0059] (S02) 7.5 g of crushed nano-alumina was dissolved in 40 mL of anhydrous ethanol solvent, 0.3 g of dispersant polyethylene glycol was added to the system for dispersion treatment, the initial stirring speed was controlled at 350 rpm, and then 0.5 g of choline chloride was added to the mixed system, the pH of the system was adjusted to 6, and then the magnetic stirring speed was reduced to 75 rpm, the system temperature was controlled at 35°C, and stirred for 1.5 hours. The product was desolventized and dried to obtain organically modified nano-alumina.

[0060] (S03) 4 g of graphite was ground with sodium chloride (2 mm), then washed and filtered to remove the sodium chloride. The dried graphite was immersed in 60 mL of 98% concentrated sulfuric acid, followed by the addition of 0.3 g of NaNO3. The initial reaction temperature was controlled at -2°C, and the magnetic stirring speed was 150 rpm. After 30 min of reaction, 2.1 g of potassium permanganate was slowly added to the system. The system temperature was controlled and slowly increased at a rate of 2°C / min until it reached 30°C. The reaction was continued for 20 min. Deionized water was then added to the reaction system in multiple portions. During the first 50 mL of deionized water, the addition rate was controlled at 5 mL / min, and the magnetic stirring speed was controlled at 150 rpm. A total of 300 mL of deionized water was added to the solution to continuously dilute the concentration of concentrated sulfuric acid. Finally, 20 mL of 30% hydrogen peroxide solution was added to stabilize the product. The reaction was terminated by stirring for another 6 h. The product was centrifuged, washed, and dried to obtain edge-carboxylated graphite oxide.

[0061] (S04) 2.2 g of the prepared organically modified nano-alumina was mixed with 6.8 g of edge carboxyl graphite oxide, dissolved in 45 mL of anhydrous ethanol, 0.2 g of dispersant polyethylene glycol and 1 g of p-toluenesulfonic acid were added, the system temperature was controlled at 85 ° C, the magnetic stirring speed was 150 rpm, and the mixture was stirred for 4 h to obtain an organically modified component.

[0062] The preparation steps of the battery negative electrode composition in this embodiment are as follows: 0.9 g of an organic modified component, 1.6 g of N-methylpyrrolidone, 0.05 g of a binder, 0.02 g of carbon black, and 0.05 g of a thickener, sodium carboxymethyl cellulose, are mixed and stirred uniformly to obtain a battery negative electrode composition.

[0063] Among them, nano-alumina (model: MG-Al2O3-10, average particle size 10nm, pore volume 0.42-0.45cm 3 / g, specific surface area 160m 2 / g) was provided by Shanghai Maoguo Nanotechnology Co., Ltd. Diamond (60 mesh) was provided by Jiyuan Xingrui Sand Factory. Choline chloride (content 98%, pH 6.5) was provided by Shandong Fengtai Biotechnology Co., Ltd. Graphite (solid carbon content ≥80%, density 1.2g / cm 3 ) was provided by Ningbo Ding Innovation Materials Co., Ltd. Polyvinylidene fluoride (model: JX202) was provided by Nanjing Zengyun Nanomaterials Co., Ltd.

[0064] Example 4

[0065] The only difference between this embodiment and embodiment 1 is that in step (S04), 3.6 g of modified nano-alumina and 5.4 g of graphite with oxidized edge carboxyl groups are used to prepare the composite material.

[0066] The remaining steps are the same as those in Example 1.

[0067] Example 5

[0068] The difference between this embodiment and Example 1 is the different weight parts of raw materials for preparing the battery negative electrode composition. The battery negative electrode composition is made of the following raw materials in weight parts: 75 parts of organic modification component, 175 parts of N-methylpyrrolidone, 5 parts of binder polyvinylidene fluoride, 2 parts of carbon black, and 3 parts of thickener sodium carboxymethyl cellulose.

[0069] The remaining steps are the same as those in Example 1.

[0070] Comparative Example 1

[0071] The difference between this comparative example and Example 1 is that the preparation steps of the organic modified component are as follows:

[0072] (S01) 7.5 g of crushed nano-alumina was dissolved in 40 mL of anhydrous ethanol solvent, 0.3 g of polyethylene glycol was added to the system for dispersion treatment, the initial stirring speed was controlled at 350 rpm, and then 0.5 g of choline chloride was added to the mixed system, the pH of the system was adjusted to 6, and then the magnetic stirring speed was reduced to 75 rpm, the system temperature was controlled at 35°C, and stirred for 1.5 hours. The product was desolventized and dried to obtain organically modified nano-alumina.

[0073] (S02) 4 g of graphite was ground with sodium chloride (1 mm), then washed and filtered to remove the sodium chloride. The dried graphite was immersed in 60 mL of 98% concentrated sulfuric acid, and then 0.3 g of NaNO3 was added. The initial reaction system temperature was controlled at -5°C, and the magnetic stirring speed was 150 rpm. After 20 min of treatment, 2.1 g of potassium permanganate was slowly added to the system. The system temperature was controlled and slowly increased at a rate of 2°C / min. When the temperature reached 30°C, the temperature was stopped and the reaction was continued for 20 min. Deionized water was then added to the reaction system in multiple portions. During the first 50 mL of deionized water, the addition rate was controlled at 5 mL / min and the magnetic stirring speed was controlled at 150 rpm. A total of 300 mL of deionized water was added to the solution to continuously dilute the concentration of concentrated sulfuric acid. Finally, 20 mL of 25% hydrogen peroxide solution was added to the system to stabilize the product. The reaction was terminated by stirring for another 6 h. The product was centrifuged, washed, and dried to obtain edge carboxyl graphite oxide.

[0074] (S03) 3.3 g of the prepared organically modified nano-alumina was mixed with 5.7 g of graphite with edge carboxyl oxidation, dissolved in 45 mL of anhydrous ethanol, 0.2 g of dispersant polyethylene glycol and 1 g of p-toluenesulfonic acid were added, the system temperature was controlled at 75 ° C, the magnetic stirring speed was 100 rpm, and stirred for 2.5 hours to obtain an organically modified component.

[0075] The remaining steps are the same as those in Example 1.

[0076] Comparative Example 2

[0077] The only difference between this comparative example and Example 1 is that step (S03) is specifically as follows:

[0078] 4 g of graphite was ground with sodium chloride, then washed and filtered to remove the sodium chloride. The dried graphite was immersed in 60 mL of 98% concentrated sulfuric acid, followed by the addition of 0.3 g of NaNO3. The initial reaction temperature was maintained at 30°C with a magnetic stirring speed of 150 rpm. After 2 h of reaction, 2.1 g of potassium permanganate was slowly added to the system. The system temperature was controlled and slowly increased at a rate of 2°C / min until it reached 30°C. The reaction was continued for 20 min. Deionized water was then added to the reaction system in multiple portions. During the first 50 mL of deionized water, the addition rate was controlled at 5 mL / min and the magnetic stirring speed was controlled at 150 rpm. A total of 300 mL of deionized water was added to the solution to continuously dilute the concentration of concentrated sulfuric acid. Finally, 20 mL of 25% hydrogen peroxide solution was added to stabilize the product. The reaction was terminated by stirring for another 6 h. The product was centrifuged, washed, and dried to obtain edge-carboxylated graphite oxide.

[0079] The remaining steps are the same as those in Example 1.

[0080] Performance testing

[0081] Battery Assembly

[0082] The positive electrode composition slurry was prepared by mixing lithium cobalt oxide, lithium manganese oxide, acetylene black, polyvinylidene fluoride, and N-methylpyrrolidone in a ratio of 60:75:10:5:160. The slurry was coated on a 12-micron thick aluminum foil and dried at 75°C for 5 hours. The foil was then uniformly rolled and cut into 128 mm × 91 mm pieces as positive electrode sheets. The density of the positive electrode sheet was 3.4 g / cm 3 The battery negative electrode compositions prepared in Examples 1-5 and Comparative Examples 1-2 were coated onto a copper foil with a thickness of 8 μm and processed in the same manner as the positive electrode to obtain a negative electrode sheet with a density of 2.6 g / cm 3 .

[0083] The positive electrode sheet, separator, and negative electrode sheet were stacked in order to obtain a battery core, and a mixed organic liquid of ethylene carbonate and propylene carbonate (mass ratio of ethylene carbonate to propylene carbonate = 1:1.5) with a LiPF6 molar concentration of 1.5 mol / L was introduced to obtain a soft-package lithium-ion battery with a rated capacity of 5 Ah.

[0084] The diaphragm (model: Celgard2320, 20 μm) was provided by Celgard Corporation of the United States.

[0085] Normal temperature cycle test experiment

[0086] At 25°C, charge the battery to 4.2V at a constant current of 0.5C, charge it to a cutoff current of 0.05C at a constant voltage of 4.2V, and then discharge it to 3.0V at a constant current of 0.5C. The discharge capacity is recorded as C1. Repeat the charge and discharge steps to obtain the discharge capacity C1 in the Nth week. 2。

[0087] Capacity retention rate = (C2 / C1)*100%;

[0088] The test results are shown in Table 1.

[0089] Table 1 Experimental results of room temperature cycle test of soft package lithium ion batteries of Examples 1-5 and Comparative Examples 1-2

[0090]

[0091] Gas volume and titration test

[0092] The charge and discharge process of soft-pack lithium-ion batteries produces a small amount of gas, primarily HF generated during the corrosion of the SEI (solid intercalation interface) in the battery's negative electrode. After charging is complete, the gas is extracted from the battery and then subjected to an acid-base titration test. The titrant dosage can be used to measure the stability of the negative electrode SEI.

[0093] Set the experimental temperature to 25℃ and charge at a constant current to 4.2V, then charge at a constant voltage for 180min. Connect the insulating tube to the soft-package lithium-ion battery to collect the gas in the battery, and set a protective device to avoid the discharge of the battery liquid. Mix the discharged gas with 20mL of deionized water. Since the main component of the gas, HF, is extremely soluble in water, an HF aqueous solution can be obtained. Finally, titrate with 0.005mol / L sodium hydroxide solution, record the titrant, and calculate the amount of HF in the battery by conversion. The test results are as follows: Figure 1 shown.

[0094] Analysis of Examples 1-5 and Comparative Examples 1-2, combined with Table 1, shows that Example 2 exhibits the highest initial cycle efficiency and capacity retention after 500 cycles. The negative electrode composition prepared using Example 2 significantly reduces the energy barrier for lithium ion diffusion within the battery's negative electrode, resulting in minimal lithium ion loss throughout the battery cycle. Under a 0.2C / 3C rate test, Example 3 exhibits the highest capacity retention, demonstrating that the negative electrode composition prepared using the formulation and experimental procedures of Example 3 exhibits the best adaptability to charge-discharge cycles.

[0095] Analyze Examples 1-5 and Comparative Examples 1-2 and combine Figure 1It can be seen that the soft-package lithium-ion battery prepared by the solution of Example 2 has the lowest gas volume. Combined with the titration line graph, it can be inferred that the electrode composition prepared in Example 2 has the most stable SEI formed at the negative electrode after charge and discharge.

[0096] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A non-solid-state lithium-ion battery using LiPF6 as a conductive salt, wherein the negative electrode of the battery is prepared using a battery negative electrode composition, characterized in that: The battery negative electrode composition is prepared from the following raw materials in parts by mass: 150-180 parts of N-methylpyrrolidone, 75-90 parts of an organic modification component, 3-5 parts of a binder, 3-5 parts of a thickener, and 1-2 parts of carbon black; The organic modified component is prepared by the following steps: (S01) mixing nano-alumina, water, and abrasive, subjecting the mixture to ultrasonic crushing, filtering impurities, and drying to obtain crushed nano-alumina; (S02) dissolving and dispersing the crushed nano-alumina, stirring for the first time, adding choline chloride, adjusting the pH and temperature, stirring for the second time, and removing the solvent and drying the treated product to obtain organically modified nano-alumina; (S03) adding graphite to abrasive, grinding, washing and filtering, taking the precipitate and adding it to concentrated sulfuric acid for acid leaching, adding NaNO3, controlling the initial reaction temperature, stirring, then adding potassium permanganate to the system, heating, diluting with water, and finally adding hydrogen peroxide solution, the product is centrifuged, the precipitate is washed and dried to obtain edge carboxyl graphite oxide; (S04) mixing and dissolving the organically modified nano-alumina and the edge carboxyl graphite oxide, adding a dispersant and a catalyst, and heating the mixture to obtain an organically modified component; the mass ratio of the organically modified nano-alumina to the edge carboxyl graphite oxide is 1:(1.5-3.5); the catalyst is p-toluenesulfonic acid; the heating treatment operation is as follows: heating the temperature to 75-85°C, the magnetic stirring speed is 100-150 rpm, and the duration is 2.5-4 hours.

2. A non-solid-state lithium-ion battery using LiPF6 as a conductive salt according to claim 1, characterized in that: In the step (S01), the abrasive is 60-mesh corundum.

3. The non-solid-state lithium-ion battery using LiPF6 as a conductive salt according to claim 1, characterized in that: In the step (S01), the ultrasonic crushing treatment time is 2-3 hours.

4. The non-solid-state lithium-ion battery using LiPF6 as a conductive salt according to claim 1, characterized in that: In the step (S02), the first stirring speed is 200-350 rpm, and the second stirring speed is 50-75 rpm; the pH is adjusted to 6-6.5 and the temperature is 35-40°C.

5. The non-solid-state lithium-ion battery using LiPF6 as a conductive salt according to claim 1, characterized in that: In the step (S03), the abrasive is sodium chloride, and the particle size is ≥1 mm.

6. The non-solid-state lithium-ion battery using LiPF6 as a conductive salt according to claim 1, characterized in that: In the step (S03), the initial reaction temperature is set to -5 to -2°C, and the stirring is performed for 20-30 minutes; the mass concentration of the hydrogen peroxide solution is 25%-30%.

7. The non-solid-state lithium-ion battery using LiPF6 as a conductive salt according to claim 1, characterized in that: In the step (S04), the dispersant is one of sodium lauryl sulfate, sodium tripolyphosphate, polyvinyl alcohol, and polyethylene glycol.

8. A method for preparing a battery negative electrode composition, for preparing a battery negative electrode composition for a non-solid-state lithium-ion battery using LiPF6 as a conductive salt as claimed in any one of claims 1 to 7, characterized in that: The steps include: The organic modified component, N-methylpyrrolidone, a binder, carbon black and a thickener are mixed and stirred uniformly to obtain a battery negative electrode composition.

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