A prelithiated conductive coating slurry and a method of making the same

Abstract

This invention relates to the field of lithium battery technology and discloses a pre-lithiated conductive coating slurry and its preparation method. The pre-lithiated conductive coating slurry prepared by this invention is made of a binder, pre-lithiated nanomaterials, graphite, a conductive agent, and deionized water. This coating slurry can compensate for irreversible lithium loss during the first cycle of the battery, thereby improving the first coulombic efficiency. At the same time, it can also improve the conductivity of the battery anode material, maintain electrochemical stability, and improve cycle performance.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, specifically to a pre-lithiated conductive coating slurry and its preparation method. Background Technology

[0002] With the rapid development of portable electronic devices, electric vehicles, and large-scale energy storage systems, the market demands continuously increasing energy density for lithium-ion batteries. One key path to improving battery energy density lies in using high-specific-capacity negative electrode active materials, such as silicon-based, tin-based, or hard carbon materials. However, during the first charge-discharge cycle, these materials consume a significant amount of lithium ions from the positive electrode due to factors such as the formation of a large solid electrolyte interface film, electrolyte decomposition, and irreversible structural changes in the material itself, leading to a significant decrease in the battery's initial coulombic efficiency. This irreversible lithium loss not only directly reduces the amount of active lithium available for subsequent cycles, forcing actual battery designs to increase the amount of positive electrode material or use a positive electrode with excess lithium content for compensation, but also severely restricts the effective improvement of the overall battery energy density.

[0003] To address these challenges, pre-lithiation technology has emerged. Current technologies primarily include methods such as direct contact between the negative electrode and lithium metal foil, adding stabilized lithium metal powder, or using chemical / electrochemical pre-lithiation reagents. However, these methods generally suffer from drawbacks such as poor process compatibility, stringent operating environment requirements, high safety risks, or difficulty in controlling the uniformity of lithium replenishment. Therefore, developing a pre-lithiation additive that is highly stable, compatible with existing slurry coating processes, and can simultaneously maintain or even enhance the electrode's conductive structure is crucial for promoting the industrialization of high-efficiency, high-energy-density lithium-ion batteries. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a pre-lithiated conductive coating slurry and its preparation method.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for preparing a pre-lithiated conductive coating slurry includes the following steps: Step S1: Add the adhesive to deionized water and mix well to obtain the premixed solution; Step S2: Add the pre-lithiated nanomaterials, graphite and conductive agent to the above premixed liquid and mix and stir evenly to obtain the pre-lithiated conductive coating slurry. Furthermore, the mass ratio of the above-mentioned binder, pre-lithiated nanomaterials, graphite, and conductive agent is 2-4:15-25:80-90:0.5-1.5, and the solid content in the slurry is 35%-45%; Furthermore, the adhesive is one of sodium alginate or sodium carboxymethyl cellulose; Furthermore, the conductive agent is one of graphene oxide, carbon nanotubes, or conductive carbon black; Furthermore, the pre-lithiated nanomaterial is a polypyrrole-coated pre-lithiated mSiO2@C nanomaterial, which is prepared by calcining mSiO2@C nanomaterial and lithium hydroxide at high temperature, and the mSiO2@C nanomaterial is obtained by calcining polydopamine-coated mesoporous silica.

[0006] Furthermore, the pre-lithiated nanomaterial is prepared specifically by the following steps: Step A1: Disperse F127 (template agent) in a mixture of ethanol and deionized water, add dopamine hydrochloride while stirring continuously until homogeneous, then add mesoporous silica (mSiO2) and disperse evenly, then add ammonia water and stir for 1.5-2.5 hours. Filter to collect the product and dry it, then transfer it to a tube furnace for high-temperature calcination and cool to room temperature to obtain mSiO2@C nanomaterials. Furthermore, the high-temperature calcination in step A1 is carried out in two stages: first, the temperature is increased to 350°C at a heating rate of 2°C / min and held for 2 hours, and then the temperature is increased to 600°C at a heating rate of 5°C / min and held for 2 hours, both of which are carried out under argon atmosphere. Furthermore, in step A1, the ratio of F127, ethanol, deionized water, dopamine hydrochloride, mesoporous silica, and ammonia is 1.5-2g:60mL:100mL:0.8-1.2g:0.5g:1.2-1.5mL; Furthermore, the mSiO2@C nanomaterial uses mesoporous silica as the core, dopamine hydrochloride as the raw material, and a polydopamine layer containing a template agent is coated on its surface. After high-temperature calcination, the template agent is removed to obtain a polydopamine carbon layer containing mesoporous material. Step A2: Grind mSiO2@C nanomaterials and lithium hydroxide thoroughly in a mortar, mix well, transfer to a tube furnace, introduce argon gas, and heat to 650-750℃ at a rate of 5℃ / min, hold for 2.5-3.5h, cool naturally to room temperature, collect the product and grind it to obtain pre-lithiated mSiO2@C nanomaterials. Furthermore, in step A2, the molar ratio of mSiO2 to lithium hydroxide in the mSiO2@C nanomaterial is 1:2.1-2.4; Furthermore, the lithium silicate formed by calcining mesoporous silica and lithium hydroxide at high temperature in step A2 is mainly the Li2SiO3 phase. Li2SiO3 can serve as a lithium source, directly replenishing the Li in the first cycle on the negative electrode surface. + The irreversible losses are reduced, thereby improving the initial coulomb efficiency; Step A3: Disperse the pre-lithiated mSiO2@C nanomaterials and p-toluenesulfonic acid in deionized water using ultrasonication, then place the mixture in an ice-water bath. Add pyrrole monomer and 3-pyrrole carboxylic acid under stirring. After stirring for 30 min, slowly add 0.35 mol / L ammonium persulfate aqueous solution and continue stirring for 12 h. Filter, wash, and freeze dry to obtain the pre-lithiated nanomaterials. Furthermore, in step A3, the ratio of the amount of pre-lithiated mSiO2@C nanomaterial, p-toluenesulfonic acid, deionized water, pyrrole monomer, and 3-pyrrolecarboxylic acid and ammonium persulfate aqueous solution is 1g:0.6-0.8g:100mL:0.3-0.4g:0.1-0.2g:10mL.

[0007] The present invention also discloses a pre-lithiated conductive coating slurry prepared by the preparation method described above.

[0008] The beneficial effects of this invention are: The pre-lithiated conductive coating slurry prepared by this invention is made of binder, pre-lithiated nanomaterials, graphite, conductive agent and deionized water. This coating slurry can compensate for irreversible lithium loss in the first cycle of the battery, thereby improving the first coulombic efficiency. At the same time, it can also improve the conductivity of the battery anode material, maintain electrochemical stability and cycle performance.

[0009] The pre-lithiated nanomaterials prepared in this invention, when introduced into a conductive coating slurry, can utilize the Li₂SiO₃ contained within them as a "lithium reserve," releasing lithium ions during the initial battery cycle. This directly replenishes the lithium ions released during the first charge-discharge cycle, which causes a solid electrolyte interface film to form on the negative electrode surface, consuming a large amount of lithium ions from the positive electrode and resulting in a decrease in the initial coulombic efficiency. Therefore, the pre-lithiated nanomaterials allow more lithium to remain in the positive electrode structure after the first charge, enabling more lithium ions to return to the positive electrode during subsequent discharges, thereby improving the initial coulombic efficiency. Because irreversible capacity is compensated, more active lithium in the positive electrode can be used for reversible cycling, thus increasing the battery's energy density. Furthermore, Li₂SiO₃, as a stable lithium source, undergoes a relatively gentle decomposition process to release lithium, helping to maintain the integrity of the electrode structure. The carbon layer, coating the Li₂SiO₃, provides a continuous electronic conduction pathway, ensuring rapid electron transfer after lithium ion release. It also acts as a physical barrier, preventing direct contact between Li₂SiO₃ and the electrolyte, avoiding side reactions and self-discharge. Furthermore, it buffers volume changes, controlling the rate of lithium ion release and preventing excessively rapid release that could lead to localized over-lithiation. The polypyrrole outer layer further enhances the overall electronic conductivity due to its excellent conductivity. Its polymer properties also contribute to the formation of a more uniform conductive network in the slurry and better contact with the negative electrode active material. In addition, the introduction of carboxyl groups in the polypyrrole outer layer works synergistically with the binder, enhancing the interfacial interaction between the coating and the current collector through chemical bonding, thereby strengthening the adhesion of the coating slurry to the current collector (copper foil). Detailed Implementation

[0010] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0011] Example 1: A method for preparing a pre-lithiated conductive coating slurry, comprising the following steps: Step S1: Add the adhesive to deionized water and mix well to obtain the premixed solution; Step S2: Add the prelithiated nanomaterials, graphite and conductive agent to the above premixed liquid and mix and stir evenly to obtain the prelithiated conductive coating slurry.

[0012] In this embodiment, the mass ratio of binder, pre-lithiated nanomaterials, graphite and conductive agent is 2:15:80:0.5, and the solid content in the slurry is 35%.

[0013] In this embodiment, the binder is sodium alginate and the conductive agent is graphene oxide.

[0014] In this embodiment, the pre-lithiated nanomaterials are prepared by the following steps: Step A1: Disperse 1.5g F127 in a mixture of 60mL ethanol and 100mL deionized water, and add 0.8g dopamine hydrochloride while stirring continuously until homogeneous. Then add 0.5g mesoporous silica and disperse it evenly. Subsequently, add 1.2mL ammonia water and stir for 1.5h. Filter to collect the product and dry it. Then transfer it to a tube furnace and heat it to 350℃ at a heating rate of 2℃ / min and hold it for 2h. Then heat it to 600℃ at a heating rate of 5℃ / min and hold it for 2h. Both heating is carried out under argon atmosphere. Cool to room temperature to obtain mSiO2@C nanomaterials. Step A2: Grind mSiO2@C nanomaterials and lithium hydroxide thoroughly in a mortar, mix well, transfer to a tube furnace, introduce argon gas, heat to 650℃ at a rate of 5℃ / min, hold for 2.5h, cool naturally to room temperature, collect the product and grind it to obtain pre-lithiated mSiO2@C nanomaterials. The molar ratio of mSiO2 to lithium hydroxide in mSiO2@C nanomaterials is 1:2.1. Step A3: Disperse 1g of pre-lithiated mSiO2@C nanomaterials and 0.6g of p-toluenesulfonic acid ultrasonically in 100mL of deionized water, then place in an ice-water bath, and add 0.3g of pyrrole monomer and 0.1g of 3-pyrrolecarboxylic acid under stirring. After stirring for 30min, slowly add 10mL of 0.35mol / L ammonium persulfate aqueous solution and continue stirring for 12h. Filter, wash, and freeze-dry to obtain the pre-lithiated nanomaterials.

[0015] Example 2: A method for preparing a pre-lithiated conductive coating slurry, comprising the following steps: Step S1: Add the adhesive to deionized water and mix well to obtain the premixed solution; Step S2: Add the prelithiated nanomaterials, graphite and conductive agent to the above premixed liquid and mix and stir evenly to obtain the prelithiated conductive coating slurry.

[0016] In this embodiment, the mass ratio of binder, pre-lithiated nanomaterials, graphite and conductive agent is 3:20:85:1, and the solid content in the slurry is 40%.

[0017] In this embodiment, the binder is sodium carboxymethyl cellulose and the conductive agent is carbon nanotubes.

[0018] In this embodiment, the pre-lithiated nanomaterials are prepared by the following steps: Step A1: Disperse 1.8g F127 in a mixture of 60mL ethanol and 100mL deionized water, and add 1g dopamine hydrochloride while stirring continuously until homogeneous. Then add 0.5g mesoporous silica and disperse evenly. Subsequently, add 1.3mL ammonia water and stir for 2h. Filter to collect the product and dry it. Then transfer it to a tube furnace and heat it to 350℃ at a heating rate of 2℃ / min and hold for 2h. Then heat it to 600℃ at a heating rate of 5℃ / min and hold for 2h. Both heating is carried out under argon atmosphere. Cool to room temperature to obtain mSiO2@C nanomaterials. Step A2: Grind mSiO2@C nanomaterials and lithium hydroxide thoroughly in a mortar, mix well, transfer to a tube furnace, introduce argon gas, heat to 700℃ at a rate of 5℃ / min, hold for 3h, cool naturally to room temperature, collect the product and grind it to obtain pre-lithiated mSiO2@C nanomaterials. The molar ratio of mSiO2 to lithium hydroxide in mSiO2@C nanomaterials is 1:2.3. Step A3: Disperse 1g of pre-lithiated mSiO2@C nanomaterials and 0.7g of p-toluenesulfonic acid ultrasonically in 100mL of deionized water, then place in an ice-water bath, and add 0.35g of pyrrole monomer and 0.15g of 3-pyrrolecarboxylic acid under stirring. After stirring for 30min, slowly add 10mL of 0.35mol / L ammonium persulfate aqueous solution and continue stirring for 12h. Filter, wash, and freeze-dry to obtain the pre-lithiated nanomaterials.

[0019] Example 3: A method for preparing a pre-lithiated conductive coating slurry, comprising the following steps: Step S1: Add the adhesive to deionized water and mix well to obtain the premixed solution; Step S2: Add the prelithiated nanomaterials, graphite and conductive agent to the above premixed liquid and mix and stir evenly to obtain the prelithiated conductive coating slurry.

[0020] In this embodiment, the mass ratio of binder, pre-lithiated nanomaterials, graphite and conductive agent is 4:25:90:1.5, and the solid content in the slurry is 45%.

[0021] In this embodiment, the binder is sodium alginate and the conductive agent is conductive carbon black.

[0022] In this embodiment, the pre-lithiated nanomaterials are prepared by the following steps: Step A1: Disperse 2g F127 in a mixture of 60mL ethanol and 100mL deionized water, and add 1.2g dopamine hydrochloride while stirring continuously until homogeneous. Then add 0.5g mesoporous silica and disperse evenly. Subsequently, add 1.5mL ammonia water and stir for 2.5h. Filter to collect the product and dry it. Then transfer it to a tube furnace and heat it to 350℃ at a heating rate of 2℃ / min and hold for 2h. Then heat it to 600℃ at a heating rate of 5℃ / min and hold for 2h. Both heating is carried out under argon atmosphere. Cool to room temperature to obtain mSiO2@C nanomaterials. Step A2: Grind mSiO2@C nanomaterials and lithium hydroxide thoroughly in a mortar, mix well, transfer to a tube furnace, introduce argon gas, heat to 750℃ at a rate of 5℃ / min, hold for 3.5h, cool naturally to room temperature, collect the product and grind it to obtain pre-lithiated mSiO2@C nanomaterials. The molar ratio of mSiO2 to lithium hydroxide in mSiO2@C nanomaterials is 1:2.4. Step A3: Disperse 1g of pre-lithiated mSiO2@C nanomaterials and 0.8g of p-toluenesulfonic acid in 100mL of deionized water using ultrasonication. Then place the mixture in an ice-water bath and add 0.4g of pyrrole monomer and 0.2g of 3-pyrrolecarboxylic acid under stirring. After stirring for 30min, slowly add 10mL of 0.35mol / L ammonium persulfate aqueous solution and continue stirring for 12h. Filter, wash, and freeze-dry to obtain the pre-lithiated nanomaterials.

[0023] Comparative Example 1: This comparative example is a conductive coating slurry. The difference between this example and Example 2 is that the pre-lithiated nanomaterials prepared in Example 2 were not added. All other aspects are the same.

[0024] Comparative Example 2: This comparative example is a conductive coating slurry. The difference between this example and Example 2 is that Li2SiO3 is used instead of the pre-lithiated nanomaterials prepared in Example 2. All other aspects are the same.

[0025] Comparative Example 3: This comparative example is a conductive coating slurry. The difference between this example and Example 2 is that lithium powder is used instead of the pre-lithiated nanomaterials prepared in Example 2.

[0026] The conductive coating slurries prepared in Examples 1-3 and Comparative Examples 1-3 were homogenized and coated onto the surface of copper foil, then dried to obtain the negative electrode sheet. A mixture of NCM811, acetylene black, and PVDF binder at a mass ratio of 80:12:8 was uniformly applied to aluminum foil and dried to obtain the positive electrode material. A Celgard 2400 separator was used, and a lithium battery was prepared using a 1 mol / L LiPF6 conductive salt and a solvent with DMC:DEC:EC (wt%) = 1:1:1. Charge-discharge tests and cycle stability tests were then conducted at 0.1C, followed by a capacity retention test after 500 cycles. The test results are shown in Table 1:

[0027] As can be seen from Table 1, the conductive coating slurry prepared in this invention, due to the introduction of pre-lithiated nanomaterials, not only improves the initial coulombic efficiency of the battery, but also improves the initial specific capacity and cycle stability.

[0028] The above content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the scope defined by the inventive concept, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a pre-lithiated conductive coating slurry, characterized in that, Includes the following steps: Step S1: Add the adhesive to deionized water and mix well to obtain the premixed solution; Step S2: Add the pre-lithiated nanomaterials, graphite and conductive agent to the above premixed liquid and mix and stir evenly to obtain the pre-lithiated conductive coating slurry. The mass ratio of the binder, pre-lithiated nanomaterials, graphite, and conductive agent is 2-4:15-25:80-90:0.5-1.5, and the solid content in the slurry is 35%-45%. The pre-lithiated nanomaterial is a polypyrrole-coated pre-lithiated mSiO2@C nanomaterial, which is prepared by calcining mSiO2@C nanomaterial and lithium hydroxide at high temperature. The mSiO2@C nanomaterial is obtained by calcining polydopamine-coated mesoporous silica.

2. The method for preparing a pre-lithiated conductive coating slurry according to claim 1, characterized in that, The pre-lithiated nanomaterials are prepared by the following steps: Step A1: Disperse F127 in a mixture of ethanol and deionized water, add dopamine hydrochloride while stirring continuously until homogeneous, then add mesoporous silica and disperse evenly, then add ammonia and stir for 1.5-2.5 hours. Filter to collect the product and dry it, then transfer it to a tube furnace for high-temperature calcination and cool to room temperature to obtain mSiO2@C nanomaterials. Step A2: Grind mSiO2@C nanomaterials and lithium hydroxide thoroughly in a mortar, mix well, transfer to a tube furnace, introduce argon gas, and heat to 650-750℃ at a rate of 5℃ / min, hold for 2.5-3.5h, cool naturally to room temperature, collect the product and grind it to obtain pre-lithiated mSiO2@C nanomaterials. Step A3: The pre-lithiated mSiO2@C nanomaterials and p-toluenesulfonic acid are ultrasonically dispersed in deionized water, then placed in an ice-water bath. Pyrrole monomers and 3-pyrrole carboxylic acid are added under stirring. After stirring for 30 min, 0.35 mol / L ammonium persulfate aqueous solution is slowly added and stirred continuously for 12 h. After filtration, washing, and freeze-drying, the pre-lithiated nanomaterials are obtained.

3. The method for preparing a pre-lithiated conductive coating slurry according to claim 2, characterized in that, In step A1, the high-temperature calcination is carried out in two stages: first, the temperature is increased to 350℃ at a heating rate of 2℃ / min and held for 2 hours, and then the temperature is increased to 600℃ at a heating rate of 5℃ / min and held for 2 hours, both of which are carried out under argon atmosphere.

4. The method for preparing a pre-lithiated conductive coating slurry according to claim 2, characterized in that, In step A1, the ratio of F127, ethanol, deionized water, dopamine hydrochloride, mesoporous silica, and ammonia is 1.5-2g:60mL:100mL:0.8-1.2g:0.5g:1.2-1.5mL.

5. The method for preparing a pre-lithiated conductive coating slurry according to claim 2, characterized in that, In step A2mSiO2@C nanomaterials, the molar ratio of mSiO2 to lithium hydroxide is 1:2.1-2.

4.

6. The method for preparing a pre-lithiated conductive coating slurry according to claim 2, characterized in that, In step A3, the ratio of pre-lithiated mSiO2@C nanomaterials, p-toluenesulfonic acid, deionized water, pyrrole monomer, 3-pyrrolecarboxylic acid, and ammonium persulfate aqueous solution is 1g:0.6-0.8g:100mL:0.3-0.4g:0.1-0.2g:10mL.

7. The method for preparing a pre-lithiated conductive coating slurry according to claim 1, characterized in that, The binder is either sodium alginate or sodium carboxymethyl cellulose.

8. The method for preparing a pre-lithiated conductive coating slurry according to claim 1, characterized in that, The conductive agent is one of graphene oxide, carbon nanotubes, or conductive carbon black.

9. A pre-lithiated conductive coating slurry, characterized in that, The pre-lithiated conductive coating slurry is prepared according to any one of claims 1-8.

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