Lithium ion negative electrode slurry based on mesoporous alumina composite conductive agent, lithium ion negative electrode plate and preparation method

Abstract

The invention provides lithium ion negative electrode slurry based on a mesoporous alumina composite conductive agent, a lithium ion negative electrode plate and a preparation method, and belongs to the technical field of lithium ion batteries. The lithium ion negative electrode slurry comprises 95-97 parts by mass of graphite; 0.5 to 1.5 parts by mass of a composite conductive agent; 0.2 to 0.4 part by mass of sodium carboxymethyl cellulose; 1.3 to 1.7 parts by mass of polyacrylic acid; 0.4 to 0.6 part by mass of styrene butadiene rubber; wherein the composite conductive agent comprises carbon black and mesoporous alumina, and the mesoporous alumina and the carbon black form an ion-electron bicontinuous channel, so that transmission obstruction of lithium ions between a negative electrode and an electrolyte can be reduced, damage of a graphite structure in battery circulation can be inhibited, and falling and pulverization of graphite particles can be reduced; therefore, the effect of improving the negative electrode material is achieved.

Description

Technical Field

[0001] The present disclosure belongs to the technical field of lithium-ion batteries, and particularly relates to a lithium-ion negative electrode slurry based on a mesoporous alumina composite conductive agent, a lithium-ion negative electrode sheet, and a preparation method. Background Art

[0002] As the current mainstream energy storage technology, the performance optimization of lithium-ion batteries is one of the core research directions in the field of new energy. As a key component of lithium-ion batteries, the negative electrode material plays a decisive role in the overall performance of the battery. Graphite negative electrode materials have become the most widely used negative electrode materials in commercial lithium-ion batteries due to their outstanding characteristics such as high crystallinity, moderate interlayer spacing, low lithium insertion potential and stable platform, abundant resources and low price. However, the lithium ion diffusion and interface stability of graphite negative electrodes still need to be further improved to meet the requirements of high energy density, fast charging and long life. To this end, conductive additives (such as Super P carbon black, SP) are often introduced in electrode preparation to construct a conductive network and reduce the internal resistance of the electrode.

[0003] While SP, as a conductive additive, improves the performance of graphite anode materials to a certain extent, it also introduces some new challenges. First, as a carbon-based material, SP is susceptible to oxidation reactions with the electrolyte under high voltage or high temperature conditions, generating byproducts with high interfacial impedance (such as carbonate decomposition products), which accelerate capacity decay. Second, SP has a weak bonding strength with the adhesive. During long charge and discharge cycles, the volume expansion of graphite particles (10%) can easily lead to a break in the conductive network, causing SP particles to detach from the active material surface and resulting in failure of the electron transport path. Furthermore, SP's low hardness makes it difficult to alleviate stress concentration in the electrode during cycling, exacerbating the problem of electrode pulverization. Summary of the Invention

[0004] The present disclosure aims to solve at least one of the technical problems existing in the prior art and provide a lithium ion negative electrode slurry, a lithium ion negative electrode sheet and a preparation method based on a mesoporous alumina composite conductive agent.

[0005] In one aspect of the present disclosure, a lithium ion negative electrode slurry based on a mesoporous alumina composite conductive agent is provided, wherein the lithium ion negative electrode slurry comprises: 95-97 parts by mass of graphite; 0.5-1.5 parts by mass of a composite conductive agent; 0.2-0.4 parts by mass of sodium carboxymethyl cellulose; 1.3-1.7 parts by mass of polyacrylic acid; 0.4-0.6 parts by mass of styrene-butadiene rubber; wherein, The composite conductive agent comprises carbon black and mesoporous alumina, and the mesoporous alumina and the carbon black form an "ion-electron" double continuous channel.

[0006] Optionally, the content ratio of the mesoporous alumina to the carbon black is 1:1.

[0007] Optionally, the nanopore size of the mesoporous alumina is less than 500 nm.

[0008] Optionally, the content of the graphite is 96.7 parts by mass; The content of the composite conductive agent is 1 part by mass; The content of the sodium carboxymethyl cellulose is 0.3 parts by mass; The content of the polyacrylic acid is 1.5 parts by mass; The content of the styrene-butadiene rubber is 0.5 parts by mass.

[0009] In another aspect of the present disclosure, a lithium-ion negative electrode sheet is provided. The lithium-ion negative electrode sheet includes a copper foil and an electrode film disposed on the copper foil. The electrode film is formed using the lithium-ion negative electrode slurry described above.

[0010] Another aspect of the present disclosure provides a method for preparing a lithium-ion negative electrode sheet, the method comprising: Graphite, composite conductive agent, sodium carboxymethyl cellulose, polyacrylic acid and styrene-butadiene rubber are formed into a lithium ion negative electrode slurry; The lithium ion negative electrode slurry is evenly coated on the surface of the copper foil, and the copper foil with the slurry is dried and punched to obtain a lithium ion negative electrode sheet.

[0011] Optionally, the drying temperature is 90-110° C., and the drying time is 0.5-1.5 hours.

[0012] Optionally, the radius of the lithium-ion negative electrode sheet is 5-10 mm.

[0013] The present disclosure provides a lithium-ion negative electrode slurry, a lithium-ion negative electrode sheet, and a preparation method based on a mesoporous alumina composite conductive agent. The lithium-ion negative electrode slurry comprises: 95-97 parts by mass of graphite; 0.5-1.5 parts by mass of a composite conductive agent; 0.2-0.4 parts by mass of sodium carboxymethyl cellulose; 1.3-1.7 parts by mass of polyacrylic acid; and 0.4-0.6 parts by mass of styrene-butadiene rubber. The composite conductive agent comprises carbon black and mesoporous alumina. The mesoporous alumina and the carbon black form a continuous "ion-electron" bichannel, which can reduce the transport barrier of lithium ions between the negative electrode and the electrolyte, inhibit the destruction of the graphite structure during battery cycling, and reduce the shedding and pulverization of graphite particles, thereby achieving the effect of improving the negative electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a flowchart of a method for preparing a lithium-ion negative electrode slurry based on a mesoporous alumina composite conductive agent according to a specific embodiment of the present disclosure; Figure 2 This is a SEM image of the negative electrode sheet of Example 1 of the present disclosure; Figure 3 The performance diagram of the lithium-ion battery of Example 1 and Comparative Examples 1-2 of the present disclosure; Figure 4 Schematic diagram of a three-dimensional dual transmission network formed on the graphite surface by mesoporous alumina and SP as a composite conductive agent in Example 1 of the present disclosure; Figure 5 This is a SEM image of the negative electrode sheet of Comparative Example 1 of the present disclosure; Figure 6 This is the SEM image of the negative electrode sheet of Comparative Example 2 of the present disclosure. DETAILED DESCRIPTION

[0015] To enable those skilled in the art to better understand the technical solutions of the present disclosure, the present disclosure is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to illustrate the present disclosure and are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present disclosure.

[0016] In one aspect of the present disclosure, a lithium ion negative electrode slurry based on a mesoporous alumina composite conductive agent is proposed, which includes: 95-97 parts by mass of graphite; 0.5-1.5 parts by mass of a composite conductive agent; 0.2-0.4 parts by mass of sodium carboxymethyl cellulose; 1.3-1.7 parts by mass of polyacrylic acid; and 0.4-0.6 parts by mass of styrene-butadiene rubber; wherein the composite conductive agent includes carbon black and mesoporous alumina, and the mesoporous alumina and the carbon black form an "ion-electron" double continuous channel. In this embodiment, mesoporous alumina and carbon black are used as composite conductive agents, wherein mesoporous alumina, with its high specific surface area and three-dimensional continuous pores, significantly enhances the electrolyte wettability, promotes the diffusion kinetics of lithium ions, and constructs an efficient ion-electron dual transport network through point-to-surface contact with SP conductive carbon black; secondly, the nanoporous structure of mesoporous alumina can buffer the volume expansion of the graphite negative electrode by about 10% during the lithium insertion-delithiation process, inhibit electrode pulverization, reduce the failure of the conductive network caused by the volume change of graphite, and maintain the effectiveness of the electron transmission path; finally, mesoporous alumina has high chemical stability, which can effectively inhibit the side reaction between the electrolyte and graphite, improve the battery's gram capacity, first efficiency and cycle stability, and extend its service life. In other words, after the mesoporous alumina is composited with SP, it can synergistically construct a more stable electrode structure, relieve stress concentration, and reduce the problem of electrode pulverization.

[0017] In some preferred embodiments, the content of graphite is 96.7 parts by mass. Graphite is the main active material of the negative electrode material, and a higher content of graphite can provide sufficient lithium storage sites.

[0018] In other preferred embodiments, the content of sodium carboxymethyl cellulose (CMC) is 0.3 parts by mass, which tightly bonds components such as graphite and composite conductive agent to form a stable electrode structure. At the same time, during the preparation process, an appropriate amount of CMC can also adjust the viscosity of the slurry, giving it good fluidity and coating properties, thereby facilitating electrode coating processing.

[0019] In other preferred embodiments, the content of polyacrylic acid (PAA) is 1.5 parts by mass. Polyacrylic acid forms a strong bonding network between the graphite particles, the conductive agent and the current collector, further improving the overall structural stability of the electrode, and synergistically with other additives such as sodium carboxymethyl cellulose to further optimize the performance of the electrode.

[0020] In other preferred embodiments, the content of styrene-butadiene rubber (SBR) is 0.5 parts by mass, which can improve the bonding force between the active material and the current collector, reduce the shedding of the active material during the charge and discharge process, and increase the flexibility and elasticity of the electrode, so that the electrode can better adapt to the volume changes of active materials such as graphite during the charge and discharge process, and alleviate the stress generated thereby.

[0021] In other preferred embodiments, the composite conductive agent comprises 1 part by mass, and the ratio of the mesoporous alumina to the carbon black is 1:1. Specifically, the mesoporous alumina content is preferably 0.5 part by mass, and the carbon black content is preferably 0.5 part by mass. This equalization of the two allows for the construction of an efficient ion-electron dual transport network. The high specific surface area and three-dimensional continuous pores of the mesoporous alumina enhance electrolyte wettability, promote lithium ion diffusion, and facilitate electron transport in contact with the carbon black. Furthermore, this ratio balances the ability to buffer expansion and maintain conductive network stability, suppressing electrode pulverization and ensuring charge-discharge performance.

[0022] In other preferred embodiments, the nanopore size of the mesoporous alumina is less than 500 nm. Smaller nanopore size provides a larger specific surface area, enhancing electrolyte wettability and shortening the diffusion path of lithium ions in the electrode material, thereby accelerating lithium ion transport kinetics. Furthermore, the appropriate nanopore size can better buffer the volume expansion that occurs during the lithium insertion and delithiation process of the graphite negative electrode, effectively suppressing electrode pulverization, enhancing the stability of the electrode structure, and extending the battery life.

[0023] This embodiment proposes a mesoporous alumina material and an "ion-electron" dual continuous channel constructed with SP to optimize the electrode microstructure. The mesoporous alumina is a multi-channel lithium ion transport material with high hardness and mechanical strength, high stability, and provides fast lithium ion channels. The mesoporous structure of alumina can adsorb electrolyte and accelerate the diffusion of lithium ions, forming a dual network of "alumina ion conduction + SP electron conduction" in SP, reducing the transmission barrier of lithium ions between the negative electrode and the electrolyte, inhibiting the destruction of the graphite structure during the battery cycle, and reducing the shedding and pulverization of graphite particles, thereby achieving the effect of improving the negative electrode material.

[0024] In another aspect of the present disclosure, a lithium ion negative electrode sheet is provided. The lithium ion negative electrode sheet includes a copper foil and an electrode film disposed on the copper foil. The electrode film is formed using the lithium ion negative electrode slurry described above.

[0025] like Figure 1 As shown, another aspect of the present disclosure provides a method for preparing a lithium-ion negative electrode sheet S100, which specifically includes the following steps S110-S120: S110, forming a lithium ion negative electrode slurry from graphite, a composite conductive agent, sodium carboxymethyl cellulose, polyacrylic acid, and styrene-butadiene rubber.

[0026] Specifically, graphite, mesoporous alumina, sodium carboxymethyl cellulose, polyacrylic acid and styrene-butadiene rubber are mixed in a certain proportion to form a lithium ion negative electrode slurry.

[0027] In some preferred embodiments, the content of graphite is preferably 95-97 parts by mass; the content of the composite conductive agent is preferably 0.5-1.5 parts by mass; the content of sodium carboxymethyl cellulose is preferably 0.2-0.4 parts by mass; the content of polyacrylic acid is preferably 1.3-1.7 parts by mass; the content of styrene-butadiene rubber is preferably 0.4-0.6 parts by mass; and the composite conductive agent includes carbon black and mesoporous alumina.

[0028] S120, evenly coating the lithium ion negative electrode slurry on the surface of the copper foil, drying the copper foil with the slurry, and punching it to obtain a lithium ion negative electrode sheet.

[0029] Specifically, a four-sided preparation machine is used to coat the mixed negative electrode slurry on the surface of the copper foil. After coating, the copper foil with the slurry is transferred to a vacuum drying oven at 90-110°C and dried continuously at 90-110°C to remove the solvent and ensure the slurry adheres firmly to the copper foil. Finally, a sheet puncher is used to punch the dried electrode film into discs, completing the production of the negative electrode sheet.

[0030] In some preferred embodiments, the drying temperature is preferably 90° C., 100° C., 110° C., etc., and the drying time is 0.5 hour, 1 hour, 1.5 hours, etc.

[0031] In other preferred embodiments, the radius of the lithium-ion negative electrode sheet is 5 mm, 7 mm, 10 mm, etc.

[0032] The following is a further description of the method for preparing a lithium ion negative electrode slurry and a lithium ion negative electrode sheet based on a mesoporous alumina composite conductive agent with reference to specific examples: Example 1 Negative electrode sheet fabrication: First, graphite, a composite conductive agent (mesoporous alumina and carbon black in a 1:1 ratio), sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), and styrene-butadiene rubber (SBR) are thoroughly mixed in a precise mass ratio of 96.7:1:0.3:1.5:0.5 to form a uniform black slurry. Next, a 200μm-thick four-sided preparation device is used to evenly coat the mixed black slurry on the surface of copper foil. After coating, the slurry-coated copper foil is transferred to a 100°C vacuum drying oven and dried for one hour to remove the solvent and ensure the slurry adheres firmly to the copper foil. Finally, a sheet puncher is used to punch the dried electrode film into discs with a radius of 7mm, completing the negative electrode sheet fabrication.

[0033] After preparing the aforementioned negative electrode sheet, it was used as the working electrode, metallic lithium was selected as the counter electrode, and a 1:1 volume ratio mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) with 1 mol / L lithium hexafluorophosphate (LiPF6) dissolved therein was used as the electrolyte. A polypropylene (PP) separator was used as the battery separator. These components were assembled into CR2032 button cells in a glove box atmosphere filled with argon and containing very low levels of water and oxygen. Following assembly, the cells were subjected to constant current charge and discharge tests within a voltage range of 2V to 0.001V.

[0034] The resistivity of the electrode sheet was tested on a sheet resistance meter at 25±3°C. The test results are shown in Table 1. The sheet resistivity is 4.581 g·cm -3 , the gram capacity is 350.35mAh g -1 The first cycle charge and discharge efficiency is 97.28%.

[0035] like Figure 2 As shown, both mesoporous alumina and SP can be evenly dispersed on the graphite surface.

[0036] like Figure 3 As shown in Table 1, at a rate of 0.1C, the negative electrode sheet of Example 1 has a capacity of 350.35 mAh·g -1 The charge capacity.

[0037] like Figure 4As shown, mesoporous alumina and SP form a double network of "alumina conducting ions + SP conducting electrons".

[0038] Comparative Example 1 The preparation method is the same as that of Example 1, except that the composite conductive agent is changed to mesoporous alumina.

[0039] After preparing the aforementioned negative electrode sheet, it was used as the working electrode, metallic lithium was selected as the counter electrode, and a 1:1 volume ratio mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) with 1 mol / L lithium hexafluorophosphate (LiPF6) dissolved therein was used as the electrolyte. A polypropylene (PP) separator was used as the battery separator. These components were assembled into CR2032 button cells in a glove box atmosphere filled with argon and containing very low levels of water and oxygen. Following assembly, the cells were subjected to constant current charge and discharge tests within a voltage range of 2V to 0.001V.

[0040] The resistivity of the electrode sheet was tested on a sheet resistance meter at 25±3°C. The test results are shown in Table 1. The sheet resistivity is 22.399 g·cm -3 , the gram capacity is 347.58mAh g -1 The first cycle charge and discharge efficiency is 97.23%.

[0041] like Figure 5 As shown, mesoporous alumina can be evenly dispersed on the graphite surface.

[0042] like Figure 3 As shown in Table 1, at a rate of 0.1C, the negative electrode sheet of Comparative Example 1 has a capacity of 347.58 mAh·g -1 The charge capacity.

[0043] Comparative Example 2 The preparation method is the same as that of Example 1, except that the composite conductive agent is changed to carbon black.

[0044] After preparing the aforementioned negative electrode sheet, it was used as the working electrode, metallic lithium was selected as the counter electrode, and a 1:1 volume ratio mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) with 1 mol / L lithium hexafluorophosphate (LiPF6) dissolved therein was used as the electrolyte. A polypropylene (PP) separator was used as the battery separator. These components were assembled into CR2032 button cells in a glove box atmosphere filled with argon and containing very low levels of water and oxygen. Following assembly, the cells were subjected to constant current charge and discharge tests within a voltage range of 2V to 0.001V.

[0045] The resistivity of the electrode sheet was tested on a sheet resistance meter at 25±3°C. The test results are shown in Table 1. The sheet resistivity is 2.697 g·cm -3 , the gram capacity is 350.01mAh·g -1 The first cycle charge and discharge efficiency is 96.82%.

[0046] like Figure 6 As shown in Figure 3, SP tends to aggregate in the gaps of graphite.

[0047] like Figure 3 As shown in Table 1, at a rate of 0.1C, the negative electrode sheet of Comparative Example 1 has a capacity of 350.01 mAh·g -1 The charge capacity.

[0048] Table 1 Performance test results of negative electrode sheets prepared in Examples and Comparative Examples

[0049] Analysis of the data in Table 1 shows that, compared to the negative electrode sheet prepared using the composite conductive agent in Example 1, the negative electrode sheet of Example 1 exhibits moderate resistivity, higher first-cycle charge-discharge efficiency, and higher specific charge capacity. These performance advantages effectively shorten the lithium-ion transport path within the material, significantly improving lithium-ion transport efficiency. This improved lithium-ion transport efficiency effectively ensures excellent battery performance.

[0050] It is understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present disclosure, and the present disclosure is not limited thereto. Those skilled in the art may make various modifications and improvements without departing from the spirit and substance of the present disclosure, and such modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. A lithium ion negative electrode slurry based on a mesoporous alumina composite conductive agent, characterized in that: The lithium ion negative electrode slurry comprises: 95-97 parts by mass of graphite; 0.5-1.5 parts by mass of a composite conductive agent; 0.2-0.4 parts by mass of sodium carboxymethyl cellulose; 1.3-1.7 parts by mass of polyacrylic acid; 0.4-0.6 parts by mass of styrene-butadiene rubber; wherein, The composite conductive agent includes carbon black and mesoporous alumina, and the mesoporous alumina and the carbon black form an "ion-electron" double continuous channel.

2. The lithium ion negative electrode slurry according to claim 1, characterized in that The content ratio of the mesoporous alumina to the carbon black is 1:

1.

3. The lithium ion negative electrode slurry according to claim 1, characterized in that The nanopore size of the mesoporous alumina is less than 500 nm.

4. The lithium ion negative electrode slurry according to claim 1, characterized in that The content of the graphite is 96.7 parts by mass; The content of the composite conductive agent is 1 part by mass; The content of the sodium carboxymethyl cellulose is 0.3 parts by mass; The content of the polyacrylic acid is 1.5 parts by mass; The content of the styrene-butadiene rubber is 0.5 parts by mass.

5. A lithium ion negative electrode sheet, characterized in that: The lithium ion negative electrode sheet includes a copper foil and an electrode film disposed on the copper foil, and the electrode film is formed by using the lithium ion negative electrode slurry according to any one of claims 1 to 4.

6. A method for preparing the lithium ion negative electrode sheet according to claim 5, characterized in that: The method comprises: Graphite, composite conductive agent, sodium carboxymethyl cellulose, polyacrylic acid and styrene-butadiene rubber are formed into a lithium ion negative electrode slurry; The lithium ion negative electrode slurry is evenly coated on the surface of the copper foil, and the copper foil with the slurry is dried and punched to obtain a lithium ion negative electrode sheet.

7. The method according to claim 6, characterized in that The drying temperature is 90-110° C. and the drying time is 0.5-1.5 hours.

8. The method according to claim 6, characterized in that: The radius of the lithium ion negative electrode sheet is 5-10 mm.

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