A Lithium Battery Conductive Paste and Its Preparation Method

Abstract

This application relates to the technical field of conductive pastes, and specifically discloses a lithium battery conductive paste and a preparation method thereof. A lithium battery conductive paste includes the following components in parts by weight: 20 - 35 parts of graphite, 60 - 80 parts of carbon black, 1 - 2 parts of carbon nanotubes, 1 - 2 parts of graphene, 70 - 90 parts of binder, 4 - 7 parts of polyvinylpyrrolidone, 15 - 20 parts of modified melamine resin, and 650 - 800 parts of deionized water. When the lithium battery conductive paste prepared in this application is used in a lithium battery, the lithium battery has good rate performance and cycle performance.

Description

Technical Field

[0001] The present application relates to the technical field of conductive pastes, and more specifically, to a conductive paste for lithium batteries and a preparation method thereof. Background Art

[0002] Lithium battery is an electrochemical energy storage device. Its working process is the process of mutual conversion of electrical energy and chemical energy. It is essentially a concentration difference battery. When charging, the external voltage causes the lithium ions in the positive electrode to escape, flow through the diaphragm through the electrolyte and embed into the negative electrode; when discharging, the lithium ions escape from the negative electrode, flow through the diaphragm through the electrolyte and embed into the positive electrode. The movement of lithium ions inside the battery runs through the charging and discharging process, which has a significant impact on many performances of the battery, such as capacity, rate performance, and cycle life.

[0003] Conductive paste is an important component of lithium batteries and plays an important role in the battery charging and discharging process. Conductive paste forms a stable conductive network between the electrode material particles. When the lithium battery is charged and discharged, it ensures that lithium ions can be quickly embedded in and out of the electrode material, allowing the battery to withstand more charge and discharge cycles while maintaining good performance and extending the battery's cycle life.

[0004] However, lithium batteries still face the problem of unstable rate performance and cycle performance. During the first charging process of lithium batteries, the organic solvent and lithium salt in the electrolyte will undergo a reduction reaction on the surface of the negative electrode. The products generated by these reactions will form a layer of solid electrolyte interface film on the surface of the negative electrode. This reaction is irreversible and will consume a certain amount of lithium ions, reducing the capacity of the lithium battery and further reducing the rate performance of the lithium battery.

[0005] The Chinese patent application document with publication number CN114121384A discloses a water-based conductive slurry and its preparation method and application. The patent application document first prepares nano-mesoporous spheres, then mixes the nano-mesoporous spheres, nitrogen-doped graphene and carbon nanotubes to prepare modified graphene fibers, so that the nano-mesoporous spheres, nitrogen-doped graphene and carbon nanotubes are fixed together on the loose and porous mesh fibers to prepare an efficient conductive fiber mesh structure and form an electrode conductive frame. The successful construction of the conductive fiber mesh structure improves the rate performance and cycle stability of the battery, but fails to effectively solve the problem of lithium battery capacitance reduction caused by the consumption of lithium ions during the first charging of the battery. Summary of the invention

[0006] In order to further improve the rate performance and cycle performance of lithium batteries, the present application provides a lithium battery conductive slurry and a preparation method thereof.

[0007] In a first aspect, the present application provides a lithium battery conductive paste, which adopts the following technical solution:

[0008] A lithium battery conductive paste, comprising the following components in parts by weight: 20-35 parts of graphite, 60-80 parts of carbon black, 1-2 parts of carbon nanotubes, 1-2 parts of graphene, 70-90 parts of binder, 4-7 parts of polyvinylpyrrolidone, 15-20 parts of modified melamine resin, and 650-800 parts of deionized water;

[0009] The preparation method of the modified melamine resin comprises the following steps:

[0010] (1) Mix melamine, deionized water and formaldehyde solution evenly, raise the temperature, add sodium hydroxide, react at a constant temperature, and add poloxamer 407 after the reaction ends to obtain a prepolymer resin;

[0011] (2) Mix nano lithium phosphate and prepolymer resin evenly, cure with acid, crush, wash, dry and grind to obtain lithium-embedded melamine resin;

[0012] (3) Mix ferric chloride, tetraethyl orthosilicate, ethanol and deionized water evenly, catalyze to form a gel with acid, perform solvent replacement, add ammonia water to adjust the pH, cool, add lithium-embedded melamine resin, soak, take out the lithium-embedded melamine resin after soaking treatment, dry and crush to obtain the modified melamine resin.

[0013] By adopting the above technical scheme, adding lithium-embedded modified melamine resin to the lithium battery conductive paste improves the capacitance of the lithium battery; the iron-doped silica film on the surface of the modified melamine resin improves the conductivity of the modified melamine resin and enables the lithium ions in the modified melamine resin to be embedded and removed slowly and smoothly, thereby improving the rate performance and cycle performance of the lithium battery and prolonging the service life of the lithium battery.

[0014] Preferably, in the step (2), the preparation method of nano lithium phosphate is as follows: Mix lithium carbonate solution and phosphoric acid evenly, raise the temperature for reaction, and after the reaction ends, wash and dry the product to obtain nano lithium phosphate.

[0015] By adopting the above technical scheme, the prepared nano lithium phosphate has a good crystal structure and good thermal stability, and the crystal structure is not prone to collapse during high-rate charge and discharge, which is convenient for the embedding and removal of lithium ions, makes the performance of the lithium battery more stable, and improves the rate performance of the lithium battery at the same time.

[0016] Preferably, in the step (2), the mass ratio of nano lithium phosphate to prepolymer resin is 1:(8-11).

[0017] By adopting the above technical scheme, nano lithium phosphate is evenly dispersed in the prepolymer resin to obtain a structurally stable lithium-embedded melamine resin. At the same time, lithium ions can be smoothly embedded and removed from the lithium-embedded melamine resin during charge and discharge, improving the charge and discharge efficiency of the battery, and further improving the rate performance of the lithium battery.

[0018] Preferably, in the step (2), the parameters for acid curing are as follows: the pH regulator is one of hydrochloric acid, phosphoric acid, and p-toluenesulfonic acid, the pH value is 2 - 5, the temperature is 130 - 150 °C, and the time is 20 - 30 h.

[0019] By adopting the above technical solution, the crosslinking density during the curing of melamine resin is increased, the molecular chains of melamine resin can react more fully, a strong network structure is constructed inside the melamine resin, effectively dispersing the stress generated by the insertion and extraction of lithium ions in nano lithium phosphate, reducing the lattice distortion of nano lithium phosphate, and thus improving the cycle performance of the lithium battery.

[0020] Preferably, in the step (3), the mass ratio of ferric chloride, tetraethyl orthosilicate, ethanol, and deionized water is 1:(1.8 - 2.1):(3.5 - 4):(0.35 - 0.4).

[0021] By adopting the above technical solution, the prepared silica sol has good fluidity, facilitating the formation of a uniform film on the surface of the lithium-inserted melamine resin. At the same time, introducing iron ions into the silica sol increases the conductivity of the silica sol, and the iron ions replace part of the silicon and enter the network structure. When forming a film on the surface of the lithium-inserted melamine resin, a uniform pore structure is formed. During the use of the lithium battery, the lithium ions in the modified melamine resin are inserted and extracted slowly and smoothly, improving the cycle performance and service life of the lithium battery.

[0022] Preferably, in the step (3), the process parameters for acid-catalyzed gelation are as follows: the pH regulator is one of hydrochloric acid and nitric acid, the pH value is 2 - 4, the temperature is 40 - 60 °C, and the time is 6 - 8 h.

[0023] By adopting the above technical solution, it prevents the aggregation and sedimentation of particles, improves the stability of the sol, can spread evenly during the film-forming process, the surface of the formed film is relatively flat, the film has good mechanical strength, avoids being damaged due to the internal stress of the lithium battery, and still maintains good integrity during multiple charge and discharge cycles of the lithium battery, extending the service life of the modified melamine resin, and thus improving the cycle performance of the lithium battery.

[0024] Preferably, in the step (3), the soaking time is 15 - 30 s.

[0025] By adopting the above technical solution, the surface film layer of the modified melamine resin has good integrity, uniformly controls the insertion and extraction of lithium ions in the modified melamine resin. At the same time, the surface film layer of the modified melamine resin has a relatively small thickness, reducing the hindrance to the movement of lithium ions, and thus improving the rate performance of the lithium battery.

[0026] Preferably, the binder is one of sodium carboxymethyl cellulose, polyvinyl alcohol, and polyvinylidene fluoride.

[0027] By adopting the above technical solution, the long-chain molecular structures of sodium carboxymethylcellulose, polyvinyl alcohol, and polyvinylidene fluoride can tightly bind conductive particles, helping to establish a good conductive network between the conductive particles, thereby improving the conductivity of the conductive paste. At the same time, the conductive paste becomes more stable and is not prone to sedimentation or delamination. When used in lithium batteries, the rate performance of the lithium batteries is improved.

[0028] In a second aspect, the present application provides a method for preparing a conductive paste for a lithium battery, comprising the following steps: mixing graphite, carbon black, carbon nanotubes, graphene, a binder, and deionized water evenly, and then performing sanding, and then adding a modified melamine resin and a dispersant to obtain the conductive paste for the lithium battery.

[0029] Preferably, the rotation speed of the sanding is 1500 - 2000 rpm, and the time is 3 - 5 h.

[0030] By adopting the above technical solution, the particle size of the conductive particles is effectively reduced, and the particle aggregation phenomenon caused by the existence of van der Waals forces between the conductive particles is reduced, so that the dispersibility of the conductive particles in the conductive paste is better. At the same time, the integrity of the structure of the conductive particles is maintained, avoiding the decrease in the conductivity of the conductive paste caused by the destruction of the structure of the conductive particles, enabling a complete conductive network in the conductive paste, improving the conductivity of the conductive paste, and further enhancing the rate performance of the lithium battery.

[0031] In summary, the present application has the following beneficial effects:

[0032] 1. Nano-lithium phosphate is embedded in the melamine resin. During the operation of the lithium battery, lithium ions can be extracted and embedded into the modified mesoporous melamine resin. During the charge and discharge process of the lithium battery, the amount of lithium ions embedded and extracted per unit time is increased, improving the working efficiency of the lithium battery. At the same time, the additional lithium ions introduced into the conductive paste increase the capacitance of the lithium battery; after the nano-lithium phosphate is embedded in the modified melamine resin, the lattice structure stability of the nano-lithium phosphate that allows lithium ions to freely embed and extract is enhanced, improving the capacity retention rate of the battery.

[0033] 2. Iron ions are introduced into the silica sol to improve the conductivity of the silica film and endow the silica film with a microporous structure; the silica film is coated on the surface of the lithium-embedded melamine resin, making the lithium-embedded melamine resin have a certain conductivity and enabling the embedding and extraction of lithium ions to proceed slowly, avoiding a large amount of heat generation inside the battery caused by the movement of a large number of lithium ions in a short time, damaging the battery structure, and reducing the service life of the battery. Furthermore, the capacity retention rate of the battery is improved, and the service life of the battery is extended. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the rate performance of lithium batteries assembled with the conductive paste for lithium batteries in Examples 1 - 3 and Comparative Examples 1 - 2.

[0035] Figure 2 It is a schematic diagram of the cycling performance of lithium - ion batteries assembled with the lithium - ion battery conductive paste of Examples 1 - 3 and Comparative Examples 1 - 2.

[0036] Figure 3 It is a particle size distribution diagram of the lithium - ion battery conductive paste of Examples 1 - 3 and Comparative Examples 1 - 2.

[0037] Figure 4 It is the state of the paste after ultrasonic dispersion during the preparation of the lithium - ion battery conductive paste of Example 1.

[0038] Figure 5 It is the state of the paste after sanding during the preparation of the lithium - ion battery conductive paste of Example 1.

[0039] Figure 6 It is the final state after the preparation of the lithium - ion battery conductive paste of Example 1 is completed. Detailed implementation manners

[0040] The following further elaborates on this application with reference to examples.

[0041] The raw materials of the examples and comparative examples of this application are all commercially available, unless otherwise specified.

[0042] Example 1

[0043] The lithium - ion battery conductive paste of this example is composed of the following components: 20 g of graphite, 60 g of carbon black, 1 g of carbon nanotubes, 1 g of graphene, 70 g of sodium carboxymethylcellulose, 4 g of polyvinylpyrrolidone, 15 g of modified melamine resin, and 650 g of deionized water.

[0044] The preparation method of the modified melamine resin of this example includes the following steps:

[0045] (1) Add 80 g of melamine, 128 g of deionized water, and 184 g of formaldehyde aqueous solution with a mass percentage concentration of 37% into a 500 - mL flask, stir, heat up to 80 °C, then add 0.16 g of sodium hydroxide, react for 2 h, cool to room temperature, add 1.5 g of poloxamer 407 and mix evenly to obtain a prepolymer resin.

[0046] (2) Mix 10 g of nano - lithium phosphate and 80 g of prepolymer resin, stir at room temperature, then add hydrochloric acid to adjust the pH value of the system to 2, heat up to 130 °C, react for 30 h, cool to room temperature, crush, wash with ethanol at 50 °C, dry at 60 °C, and grind to obtain the lithium - intercalated melamine resin.

[0047] (3) Mix 20 g of ferric chloride, 36 g of tetraethyl orthosilicate, 70 g of ethanol, and 7 g of deionized water uniformly. Then add hydrochloric acid to adjust the pH to 2, heat up to 40 °C, stir and react for 8 h. Add 150 g of deionized water and mix uniformly. Rotate and evaporate under reduced pressure at 70 °C for 40 min. Add ammonia water to adjust the pH to 8, cool to room temperature, add the lithium-inserted melamine resin and soak for 15 s. Then take out the lithium-inserted melamine resin, dry it in ventilation at 50 °C for 6 h, and pulverize to obtain the modified melamine resin.

[0048] The preparation method of the lithium phosphate nanoparticles in this example includes the following steps: Mix 200 mL of an aqueous solution of lithium carbonate with a mass percentage concentration of 18% and 200 g of an aqueous solution of phosphoric acid with a mass percentage concentration of 15% uniformly, put them into a reaction kettle, heat up to 190 °C, and keep the temperature constant for 3 h. After the reaction, wash the obtained product and dry it at 90 °C for 10 h to obtain the lithium phosphate nanoparticles.

[0049] The preparation method of the lithium battery conductive paste in this example includes the following steps: Take 20 g of graphite, 60 g of carbon black, 1 g of carbon nanotubes, 1 g of graphene, 70 g of sodium carboxymethylcellulose, 3 g of polyvinylpyrrolidone, and 650 g of deionized water, mix them, and disperse ultrasonically for 20 min. Then put them into a vacuum disperser and disperse for 3 h under the conditions of a vacuum degree of 0.09 MPa, a temperature of 10 °C, and a shear rate of 15 m / s. After the dispersion, filter, put the filtrate into a sand mill, and grind for 5 h at a rotation speed of 1500 rpm to obtain a mixture. Transfer the mixture to a vacuum disperser, add 15 g of the modified melamine resin and 1 g of polyvinylpyrrolidone, and disperse for 3 h under the conditions of a vacuum degree of 0.09 MPa, a temperature of 10 °C, and a shear rate of 20 m / s to obtain the lithium battery conductive paste.

[0050] Example 2

[0051] The lithium battery conductive paste in this example is composed of the following components: 35 g of graphite, 80 g of carbon black, 2 g of carbon nanotubes, 2 g of graphene, 90 g of polyvinyl alcohol, 7 g of polyvinylpyrrolidone, 20 g of the modified melamine resin, and 800 g of deionized water.

[0052] The preparation method of the modified melamine resin in this example includes the following steps:

[0053] (1) Add 80 g of melamine, 130 g of deionized water, and 180 g of an aqueous formaldehyde solution with a mass percentage concentration of 37% into a 500 mL flask, stir, heat up to 85 °C, then add 0.15 g of sodium hydroxide, react for 2 h, cool to room temperature, and add 1.6 g of poloxamer 407 and mix uniformly to obtain the prepolymer resin.

[0054] (2) Mix 10 g of lithium nanophosphate and 110 g of prepolymer resin, stir at room temperature, then add phosphoric acid to adjust the pH value of the system to 5, heat up to 150 °C, react for 20 h, cool to room temperature, crush, wash with ethanol at 50 °C, dry at 65 °C, and grind to obtain lithium-inserted melamine resin.

[0055] (3) Take 20 g of ferric chloride, 42 g of tetraethyl orthosilicate, 80 g of ethanol and 8 g of deionized water, mix them evenly, then add nitric acid to adjust the pH to 4, heat up to 60 °C, stir and react for 6 h, add 180 g of deionized water and mix evenly, perform rotary evaporation under reduced pressure at 70 °C for 50 min, add ammonia water to adjust the pH to 9, cool to room temperature, add the lithium-inserted melamine resin and soak for 30 s, then take out the lithium-inserted melamine resin and dry it in ventilation at 50 °C for 6 h, and crush to obtain modified melamine resin.

[0056] The preparation method of the lithium nanophosphate in this example includes the following steps: Mix 200 mL of an aqueous solution of lithium carbonate with a mass percentage concentration of 15% and 165 g of an aqueous solution of phosphoric acid with a mass percentage concentration of 15% evenly, put them into a reaction kettle, heat up to 200 °C, keep the temperature constant and react for 3 h. After the reaction, wash the obtained product and dry it at 100 °C for 10 h to obtain lithium nanophosphate.

[0057] The preparation method of the lithium battery conductive paste in this example includes the following steps: 35 g of graphite, 80 g of carbon black, 2 g of carbon nanotubes, 2 g of graphene, 90 g of polyvinyl alcohol, 5 g of polyvinylpyrrolidone, 800 g of deionized water, perform ultrasonic dispersion for 30 min, then put it into a vacuum disperser and disperse it for 3 h under the conditions of a vacuum degree of 0.095 MPa, a temperature of 15 °C and a shear rate of 15 m / s. After the dispersion, filter, put the filtrate into a sand mill and grind it for 3 h at a rotation speed of 2000 rpm to obtain a mixture. Transfer the mixture into a vacuum disperser, add 20 g of modified melamine resin and 2 g of polyvinylpyrrolidone, and disperse it for 3 h under the conditions of a vacuum degree of 0.09 MPa, a temperature of 10 °C and a shear rate of 15 m / s to obtain the lithium battery conductive paste.

[0058] Example 3

[0059] The lithium battery conductive paste in this example is composed of the following components: 25 g of graphite, 70 g of carbon black, 1.5 g of carbon nanotubes, 1.5 g of graphene, 80 g of polyvinylidene fluoride, 6 g of polyvinylpyrrolidone, 17 g of modified melamine resin, and 690 g of deionized water.

[0060] The preparation method of the modified melamine resin in this example includes the following steps:

[0061] (1) Add 80 g of melamine, 130 g of deionized water, and 184 g of formaldehyde aqueous solution with a mass percentage concentration of 37% into a 500 mL flask, stir, heat up to 80 °C, then add 0.16 g of sodium hydroxide, react for 2 h, cool to room temperature, and add 1.5 g of poloxamer 407 and mix evenly to obtain a prepolymer resin.

[0062] (2) Mix 10 g of lithium phosphate nanometer and 90 g of prepolymer resin, stir at room temperature, then add p-toluenesulfonic acid to adjust the pH value of the system to 4.5, heat up to 135 °C, react for 25 h, cool to room temperature, crush, wash with ethanol at 50 °C, dry at 60 °C, and grind to obtain lithium-inserted melamine resin.

[0063] (3) Take 20 g of ferric chloride, 40 g of tetraethyl orthosilicate, 78 g of ethanol, and 7.5 g of deionized water and mix evenly, then add hydrochloric acid to adjust the pH to 3, heat up to 45 °C, stir and react for 7 h, add 160 g of deionized water and mix evenly, perform rotary evaporation under reduced pressure at 70 °C for 45 min, add ammonia water to adjust the pH to 8.5, cool to room temperature, add lithium-inserted melamine resin and soak for 20 s, then take out the lithium-inserted melamine resin and dry it in ventilation at 50 °C for 6 h, crush to obtain modified melamine resin.

[0064] The preparation method of the lithium phosphate nanometer in this example includes the following steps: Mix 200 mL of lithium carbonate aqueous solution with a mass percentage concentration of 18% and 200 g of phosphoric acid aqueous solution with a mass percentage concentration of 15% evenly, put them into a reaction kettle, heat up to 190 °C, keep the temperature constant and react for 3 h, after the reaction is completed, wash the obtained product, and dry it at 90 °C for 10 h to obtain lithium phosphate nanometer.

[0065] The preparation method of the lithium battery conductive paste in this example includes the following steps: Take 25 g of graphite, 70 g of carbon black, 1.5 g of carbon nanotubes, 1.5 g of graphene, 80 g of polyvinylidene fluoride, 5 g of polyvinylpyrrolidone, and 690 g of deionized water, mix them and perform ultrasonic dispersion for 25 min, then put them into a vacuum disperser, disperse for 3 h under the conditions of a vacuum degree of 0.09 MPa, a temperature of 12 °C, and a shear rate of 15 m / s, after the dispersion is completed, filter, put the filtrate into a sand mill, and under the condition of a rotation speed of 1800 rpm, sand mill for 4 h to obtain a mixture, transfer the mixture into a vacuum disperser, add 17 g of modified melamine resin and 1 g of polyvinylpyrrolidone, and disperse for 3 h under the conditions of a vacuum degree of 0.09 MPa, a temperature of 10 °C, and a shear rate of 20 m / s to obtain the lithium battery conductive paste.

[0066] Comparative Example 1

[0067] The lithium battery conductive paste of this comparative example consists of the following components: 20 g of graphite, 60 g of carbon black, 1 g of carbon nanotubes, 1 g of graphene, 70 g of sodium carboxymethyl cellulose, 4 g of polyvinylpyrrolidone, 15 g of modified melamine resin, and 650 g of deionized water.

[0068] The preparation method of the modified melamine resin in this comparative example includes the following steps:

[0069] (1) Add 80 g of melamine, 128 g of deionized water, and 184 g of formaldehyde aqueous solution with a mass percentage concentration of 37% into a 500 mL flask, stir, heat up to 80 °C, then add 0.16 g of sodium hydroxide, react for 2 h, cool to room temperature, and add 1.5 g of poloxamer 407 and mix evenly to obtain a prepolymer resin.

[0070] (2) Mix 10 g of nano lithium phosphate and 80 g of prepolymer resin, stir at room temperature, then add hydrochloric acid to adjust the pH value of the system to 2, heat up to 130 °C, react for 30 h, cool to room temperature, crush, wash with ethanol at 50 °C, dry at 60 °C, and grind to obtain the modified melamine resin.

[0071] The preparation method of the nano lithium phosphate in this comparative example includes the following steps: Mix 200 mL of lithium carbonate aqueous solution with a mass percentage concentration of 18% and 200 g of phosphoric acid aqueous solution with a mass percentage concentration of 15% evenly, put them into a reaction kettle, heat up to 190 °C, keep the temperature constant and react for 3 h. After the reaction, wash the obtained product and dry it at 90 °C for 10 h to obtain nano lithium phosphate.

[0072] The preparation method of the lithium battery conductive paste of this comparative example includes the following steps: Take 20 g of graphite, 60 g of carbon black, 1 g of carbon nanotubes, 1 g of graphene, 70 g of sodium carboxymethyl cellulose, 3 g of polyvinylpyrrolidone, and 650 g of deionized water, mix them, ultrasonically disperse for 20 min, then put them into a vacuum disperser, disperse for 3 h under the conditions of a vacuum degree of 0.09 MPa, a temperature of 10 °C, and a shear rate of 15 m / s. After the dispersion, filter, put the filtrate into a sand mill, and sand mill for 5 h at a rotation speed of 1500 rpm to obtain a mixture. Transfer the mixture into a vacuum disperser, add 15 g of modified melamine resin and 1 g of polyvinylpyrrolidone, and disperse for 3 h under the conditions of a vacuum degree of 0.09 MPa, a temperature of 10 °C, and a shear rate of 20 m / s to obtain the lithium battery conductive paste.

[0073] Comparative Example 2

[0074] The lithium battery conductive paste of this comparative example consists of the following components: 20 g of graphite, 60 g of carbon black, 1 g of carbon nanotubes, 1 g of graphene, 70 g of sodium carboxymethyl cellulose, 4 g of polyvinylpyrrolidone, 15 g of nano lithium phosphate, and 650 g of deionized water.

[0075] The preparation method of lithium phosphate nanoparticles in this comparative example includes the following steps: Mix 200 mL of an aqueous lithium carbonate solution with a mass percentage concentration of 18% and 200 g of an aqueous phosphoric acid solution with a mass percentage concentration of 15% evenly, put them into a reaction kettle, heat up to 190 °C, keep the temperature constant for 3 h, wash the obtained product after the reaction, and dry it at 90 °C for 10 h to obtain lithium phosphate nanoparticles.

[0076] The preparation method of the lithium battery conductive paste in this comparative example includes the following steps: Take 20 g of graphite, 60 g of carbon black, 1 g of carbon nanotubes, 1 g of graphene, 70 g of sodium carboxymethylcellulose, 3 g of polyvinylpyrrolidone, and 650 g of deionized water, mix them, and perform ultrasonic dispersion for 20 min. Then put them into a vacuum disperser and disperse for 3 h under the conditions of a vacuum degree of 0.09 MPa, a temperature of 10 °C, and a shear rate of 15 m / s. After the dispersion is completed, filter, put the filtrate into a sand mill, and under the condition of a rotation speed of 1500 rpm, perform sand milling for 5 h to obtain a mixture. Transfer the mixture into a vacuum disperser, add 15 g of lithium phosphate nanoparticles and 1 g of polyvinylpyrrolidone, and disperse for 3 h under the conditions of a vacuum degree of 0.09 MPa, a temperature of 10 °C, and a shear rate of 20 m / s to obtain the lithium battery conductive paste.

[0077] Performance detection test

[0078] 1. Preparation of lithium battery: Mix LFP and the lithium battery conductive paste with a mass ratio of 1:10, stir magnetically for 8 h, then coat it on an aluminum foil, dry it in a dryer at 80 °C for 12 h to obtain a carbon-coated foil. Use a punch to cut the carbon-coated foil into small round pieces with a diameter of 14 mm, and keep the pressure at 0.6 MPa for 30 s. Then put the carbon-coated foil into a vacuum drying oven at 120 °C and dry it for 12 h to obtain a working electrode. Then weigh the working electrode in a glove box, use Celgard 2400 membrane as the separator, metallic lithium foil as the counter electrode, and a LiPF6 solution with a molar concentration of 1 mol / L as the electrolyte to assemble a CR2016 coin cell. The solvent of the LiPF6 solution is composed of ethylene carbonate, dimethyl carbonate, and diethyl carbonate, and their volume ratio is 1:1:1. The assembly process of the lithium battery is carried out in a sealed argon-filled glove box, and the moisture and oxygen content in the glove box are both kept within 1 ppm. The mass of the active material in the working electrode is about 3 mg.

[0079] 2. The cycle performance test of the lithium battery is carried out under the conditions of a charging current density of 1C and a discharging current density of 2C.

[0080] 3. Use a laser particle size distribution analyzer to test the particle size distribution of the lithium battery conductive pastes of Examples 1-3 and Comparative Examples 1-2 to obtain a particle size distribution diagram, as Figure 3 shown.

[0081] 4. During the preparation process of the lithium battery conductive paste in Example 1, observing the appearance of the paste, it can be observed that the dispersion of the paste becomes gradually uniform, as Figure 4 , Figure 5 and Figure 6 shown.

[0082] Analyzing Examples 1 - 3 and Comparative Examples 1 - 2 and combining with Figure 1 and Figure 2 it can be seen that the lithium battery prepared with the lithium battery conductive paste added with the modified melamine resin has better rate performance and cycling performance.

[0083] This specific embodiment is only an interpretation of the present application, and it does not limit the present application. Those skilled in the art can make modifications without creative contributions to this embodiment according to needs after reading this specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A lithium battery conductive paste, characterized in that: The invention comprises the following components in parts by weight: 20-35 parts of graphite, 60-80 parts of carbon black, 1-2 parts of carbon nanotubes, 1-2 parts of graphene, 70-90 parts of a binder, 4-7 parts of polyvinyl pyrrolidone, 15-20 parts of a modified melamine resin, and 650-800 parts of deionized water; The preparation method of the modified melamine resin comprises the following steps: (1) Mix melamine, deionized water and formaldehyde solution evenly, raise the temperature, add sodium hydroxide, react at a constant temperature, and add poloxamer 407 after the reaction to obtain a prepolymer resin; (2) mixing the nano lithium phosphate and the prepolymer resin uniformly, acid curing, crushing, washing, drying and grinding to obtain a lithium embedded melamine resin; (3) mixing ferric chloride, tetraethyl orthosilicate, ethanol and deionized water uniformly, acid catalyzing to form gel, solvent replacement, adding ammonia water to adjust the pH, cooling, adding lithium intercalated melamine resin, soaking, taking out the lithium intercalated melamine resin after soaking, drying, and crushing to obtain modified melamine resin; In the step (2), the mass ratio of nano lithium phosphate to prepolymer resin is 1:(8-11); In the step (3), the mass ratio of ferric chloride, tetraethyl orthosilicate, ethanol and deionized water is 1:(1.8-2.1):(3.5-4):(0.35-0.4).

2. The conductive paste for lithium batteries according to claim 1, characterized in that: In the step (2), the preparation method of nano lithium phosphate comprises the following steps: mixing lithium carbonate solution and phosphoric acid evenly, heating to react, and after the reaction is completed, washing and drying the product to obtain nano lithium phosphate.

3. The conductive paste for lithium batteries according to claim 1, characterized in that: In the step (2), the process parameters of acid curing are: the pH adjuster is one of hydrochloric acid, phosphoric acid and p-toluenesulfonic acid, the pH value is 2-5, the temperature is 130-150°C, and the time is 20-30h.

4. The conductive paste for lithium batteries according to claim 1, characterized in that: In the step (3), the process parameters of acid-catalyzed gelation are: the pH regulator is hydrochloric acid or nitric acid, the pH value is 2-4, the temperature is 40-60°C, and the time is 6-8h.

5. The conductive paste for lithium batteries according to claim 1, characterized in that: In the step (3), the soaking time is 15-30 seconds.

6. The conductive paste for lithium batteries according to claim 1, characterized in that: The binder is one of sodium carboxymethyl cellulose, polyvinyl alcohol and polyvinylidene fluoride.

7. A method for preparing a lithium battery conductive paste as claimed in claim 1, characterized in that: The method comprises the following steps: mixing graphite, carbon black, carbon nanotubes, graphene, a binder and deionized water uniformly, sand-milling, and then adding a modified melamine resin and a dispersant to obtain a lithium battery conductive slurry.

8. The method for preparing a lithium battery conductive paste according to claim 7, characterized in that: The rotation speed of the sand mill is 1500-2000 rpm, and the time is 3-5 hours.

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