A nano-copper composite negative electrode conductive agent and a preparation method of carbon-coated nano-copper

Abstract

This invention provides a nano-copper composite negative electrode conductive agent and a method for preparing carbon-coated nano-copper. The conductive agent comprises 40-50% carbon-coated nano-copper particles, 20-30% conductive carbon black, 10-15% carboxylated carbon nanotubes, and binders and dispersants. The key to its preparation lies in the in-situ growth of nano-copper particles with a 2-5 nm amorphous carbon coating layer via a hydrothermal-calcination method, solving the problem of copper oxidation and dissolution in the battery environment. Subsequently, the nano-copper, conductive carbon black, and carbon nanotubes are compositely dispersed with each other under inert gas protection through ball milling and ultrasonic processes to form a three-dimensional synergistic conductive network. When applied to the negative electrode of a lithium-ion battery, this conductive agent can construct an efficient electron transport path, significantly reduce polarization resistance, and improve the battery's fast-charging performance (6C charging for 10 minutes, SOC > 80%), cycle life (capacity retention > 80% after 2000 cycles), and structural stability, while also exhibiting good processability and safety.

Description

Technical Field

[0001] This invention relates to the field of lithium battery conductive agent technology, specifically to a nano-copper composite negative electrode conductive agent and a method for preparing carbon-coated nano-copper. Background Technology

[0002] Lithium-ion batteries face challenges such as increased polarization voltage, accelerated capacity decay, and shortened cycle life during fast charging, especially in demanding applications like power and energy storage. Traditional conductive agents, such as the combination of conductive carbon black and carbon nanotubes, primarily rely on carbon materials to construct the conductive network, resulting in limited electronic conductivity (typically 10). 2 -10 3 The S / m range makes it difficult to meet the extremely low electron transport impedance requirements at high rates. Furthermore, during repeated charge-discharge cycles, the volume expansion of active materials (especially silicon-based materials) can damage the conductive network, further deteriorating battery performance. In addition, while metallic copper possesses excellent electronic conductivity (>5×10⁻⁶), it is insufficient for achieving the extremely low electron transport impedance required at high rates. 6 While copper-based materials have a high electron conductivity (S / m), their nanoparticles are easily oxidized and dissolved in the battery electrolyte environment, leading to the loss of active lithium, instability of the SEI film, and even safety issues. This limits the direct application of copper-based materials in battery conductive agents. Therefore, developing a novel negative electrode conductive agent that combines ultra-high electron conductivity, excellent structural stability, and good electrochemical compatibility is crucial for improving the fast-charging performance and cycle life of batteries. Summary of the Invention

[0003] (a) Technical issues

[0004] The present invention aims to provide a nano-copper composite negative electrode conductive agent with high conductivity, high stability and long cycle life and its preparation method, so as to solve the problems of insufficient electron conduction, large polarization and poor cycle stability of existing conductive agents in fast charging applications.

[0005] (II) Technical Content

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is: a method for preparing carbon-coated nano-copper, comprising the following steps:

[0007] S1: Mix the copper salt solution with glucose to obtain a mixed solution;

[0008] S2: The mixed solution is subjected to a hydrothermal reaction at a temperature of 180-200℃ for 12-15 hours.

[0009] S3: The product after hydrothermal reaction is centrifuged, washed, and freeze-dried to obtain the precursor;

[0010] S4: The precursor is calcined under inert gas protection at a temperature of 500-550°C for 2-3 hours to obtain carbon-coated nano-copper particles.

[0011] The carbon-coated copper nanoparticles have a particle size D50 of 20-50 nm and are coated with an amorphous carbon layer with a thickness of 2-5 nm.

[0012] Furthermore, the copper salt is CuSO4; the inert gas is nitrogen.

[0013] A nano-copper composite negative electrode conductive agent is composed of the following components in mass percentage: 40-50% carbon-coated nano-copper particles; 20-30% conductive carbon black; 10-15% carbon nanotubes; 5-8% binder; 2-3% dispersant; and the balance being deionized water; wherein the carbon-coated nano-copper particles are prepared according to the preparation method described in claim 1 or 2.

[0014] Furthermore, the carbon-coated copper nanoparticles have a particle size D50 of 20-50 nm and a specific surface area of ​​30-50 m². 2 / g, purity ≥99.95%, with an amorphous carbon layer of 2-5nm thickness on the surface.

[0015] Furthermore, the conductive carbon black has a DBP absorption value ≥400 ml / 100 g and a specific surface area of ​​1200-1400 m². 2 / g.

[0016] Furthermore, the carbon nanotubes are carboxylated multi-walled carbon nanotubes with a diameter of 8-15 nm, a length of 5-20 μm, and a carboxyl content of 0.5-1.5 wt%.

[0017] Furthermore, the binder comprises sodium carboxymethyl cellulose and styrene-butadiene rubber; the dispersant is a polyethylene glycol derivative with a molecular weight of 2000±100 Da.

[0018] A method for preparing a nano-copper composite conductive agent includes the following steps:

[0019] Pre-dispersion: A portion of deionized water, dispersant, and sodium carboxymethyl cellulose from the binder are mixed and dispersed by high-speed shearing.

[0020] Dispersion of nano-copper: Add the carbon-coated nano-copper particles to the mixture obtained in the previous step, and then disperse by ball milling;

[0021] Dispersion of conductive materials: Add conductive carbon black and carbon nanotubes sequentially to the slurry obtained in the previous step, and then perform ultrasonic treatment;

[0022] Slurry preparation: Add the remaining binder to the slurry obtained in the previous step, stir at low speed, and adjust the viscosity to 3000±500mPa·s at a temperature of 25℃ to obtain the conductive agent slurry.

[0023] Furthermore, the ball mill uses zirconia balls, rotates at 300 rpm, and lasts for 2 hours; the ultrasonic treatment has a frequency of 40 kHz, a power of 800 W, and a duration of 1 hour.

[0024] Furthermore, the method includes the following steps: spray drying the conductive agent slurry at an inlet temperature of 200°C and an outlet temperature of 90°C to obtain a dried powder; subsequently, the dried powder is subjected to airflow pulverization and sieving under inert gas protection to obtain the finished conductive agent.

[0025] (III) Technical Effects

[0026] The advantages of this invention compared to the prior art are:

[0027] 1. The carbon-coated copper nanoparticles prepared in this invention serve as the core conductive phase, exhibiting ultra-high conductivity (>5×10⁻⁶). 6 The S / m structure constructs a "highway" for electron transport, forming a three-dimensional synergistic conductive network with conductive carbon black (SP) and carboxylated carbon nanotubes (CNTs), significantly reducing the charge transfer impedance and polarization voltage of the electrode. Under 6C fast charging conditions, the capacity retention rate exceeds 88% after charging to over 80% SOC in 10 minutes, and the capacity retention rate is still above 80% after 2000 cycles under 1C charge-discharge conditions, far exceeding the traditional SP / CNT conductive agent system.

[0028] 2. A uniform and dense 2-5 nm amorphous carbon layer was coated onto the surface of nano-copper using a hydrothermal-calcination in-situ growth technique. This carbon layer, while maintaining high lithium-ion conductivity, effectively isolates the electrolyte from direct contact with copper, inhibiting copper oxidation (Cu). 0 →Cu 2+ The ion dissolution (dissolution amount <0.5ppm) stabilizes the SEI membrane, ensuring its electrochemical stability and safety under long-term cycling.

[0029] 3. The synergistic effect of carboxylated CNTs and PEG dispersants in the conductive agent improves the dispersion stability (Zeta potential ≤ -40mV) and processability of the slurry (solid content up to 50%). The formed three-dimensional network has good mechanical elasticity, which can effectively buffer the volume expansion of silicon-carbon anodes during cycling (expansion rate <15%) and maintain the integrity of the conductive network.

[0030] 4. Although the core material, nano-copper, is more expensive, its extremely high conductivity means that only 1.5-2.0 wt% needs to be added to the negative electrode (compared to 3-4 wt% for traditional carbon-based conductive agents). Furthermore, improved slurry rheology increases coating speed and reduces drying energy consumption. From a battery system perspective, the overall total cost of ownership (TCO) is more advantageous due to increased energy density and cycle life. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Example 1

[0032] This embodiment provides a nano-copper composite negative electrode conductive agent and its preparation method, the specific steps of which are as follows:

[0033] Step 1: Preparation of carbon-coated copper nanoparticles

[0034] Weigh 10g of copper sulfate pentahydrate (CuSO4·5H2O), dissolve it in 200mL of deionized water to prepare a copper salt solution; add 5g of glucose as a carbon source to the above copper salt solution, stir magnetically until completely dissolved to form a homogeneous mixture; transfer the mixture to a 500mL stainless steel hydrothermal reactor lined with polytetrafluoroethylene, seal it, and place it in an oven at 180℃ for 12 hours; after the reaction is complete, allow it to cool naturally to room temperature, centrifuge the obtained products, and separate them using... The sample was washed three times with deionized water and anhydrous ethanol to remove impurities. The washed precipitate was freeze-dried for 24 hours to obtain precursor powder. The precursor powder was placed in a tube furnace and heated to 500℃ at a rate of 5℃ / min under continuous high-purity nitrogen gas (flow rate 200 mL / min, oxygen content <0.1 ppm), and calcined at this temperature for 2 hours. After calcination, the furnace was cooled to room temperature, and the product was collected under a nitrogen atmosphere to obtain carbon-coated copper nanoparticles. TEM analysis showed that the average particle size (D50) was approximately 35 nm, and the thickness of the amorphous carbon layer on the surface was approximately 3 nm. XPS analysis showed that Cu... 0 Price status ratio ≥ 99.5%.

[0035] Step 2: Preparation of composite conductive agent slurry

[0036] Pre-dispersion: Operate in an inert atmosphere glove box (dew point < -40℃, O2 < 0.1ppm). Add 450g of deionized water to the stirred tank of a high-speed shear disperser, then add 15g of polyethylene glycol-2000 (PEG-2000) dispersant and 15g of sodium carboxymethyl cellulose (CMC, viscosity approximately 2000 mPa·s, half the total CMC amount). Turn on the disperser and shear at 2000 rpm for 30 minutes to obtain a homogeneous premix.

[0037] Nano-copper dispersion: Add 250g of the carbon-coated nano-copper powder prepared in the first step to the premix. Transfer the material to a planetary ball mill, add zirconia grinding balls (ball-to-material ratio of 10:1), and ball mill at 300 rpm for 2 hours.

[0038] Addition of conductive materials: Transfer the ball-milled slurry back to the mixing vessel, and add 150g of conductive carbon black (SP, Ketjenblack EC-600JD, DBP absorbance 420ml / 100g) and 75g of carboxylated multi-walled carbon nanotubes (CNTs, diameter 10nm, length 10μm, carboxyl content 1.0wt%) sequentially. Then, place the slurry in an ultrasonic cell disruptor and sonicate at 40kHz frequency and 800W power for 1 hour.

[0039] Adding binder and preparing the slurry: Add the remaining 15g CMC and 40g styrene-butadiene rubber (SBR) emulsion (40% solids content) to the ultrasonicated slurry. Reduce the stirring speed to 500 rpm and stir at low speed for 30 minutes to ensure thorough mixing of all components. Use a rotational viscometer (25℃) to measure the slurry viscosity and fine-tune the amount of deionized water to control the final slurry viscosity at approximately 3200 mPa·s.

[0040] The resulting slurry had a uniform appearance, no visible agglomerates, a solid content of approximately 50 wt%, and a zeta potential of -43 mV.

[0041] Step 3: Drying and Finished Product Processing

[0042] The above slurry was spray-dried. The inlet air temperature was set to 200℃ and the outlet air temperature to 90℃, and the feed rate was controlled by a peristaltic pump. The dried composite conductive agent powder was collected; the spray-dried powder was placed in an air jet mill and pulverized under a nitrogen atmosphere, with the pulverization pressure controlled so that the final powder particle size D50 was approximately 6μm; the powder was sieved through a 400-mesh sieve (approximately 38μm aperture) to remove any possible small amounts of large particles; the sieved finished powder was quickly packed into aluminum foil bags with sealing strips, vacuumed, filled with argon, sealed, and stored in a dry environment. Example 2

[0043] This embodiment provides another formulation of nano-copper composite negative electrode conductive agent, focusing on demonstrating the preparation process under different nano-copper contents.

[0044] Step 1: Preparation of carbon-coated copper nanoparticles

[0045] This step is the same as the first step in Example 1, and carbon-coated copper nanoparticles of the same specifications are prepared.

[0046] Step 2: Preparation of composite conductive agent slurry

[0047] Pre-dispersion: Under the same inert atmosphere, add 470g of deionized water to the stirred tank, then add 12g of PEG-2000 dispersant and 18g of CMC (half of the total CMC amount, viscosity approximately 2500mPa·s). Perform high-speed shearing at 2000rpm for 30 minutes.

[0048] Dispersion of nano-copper: Add 200g of carbon-coated nano-copper powder to the premix. Ball mill under the same conditions (300rpm, 2 hours).

[0049] Addition of conductive materials: 180g of conductive carbon black (SP) of the same type and 90g of carboxylated multi-walled carbon nanotubes (CNTs) of the same specifications were added sequentially. Then, ultrasonic treatment was performed (40kHz, 800W, 1 hour).

[0050] Binder addition and slurry preparation: Add the remaining 18g CMC and 32g SBR emulsion. Stir at low speed (500rpm) for 30 minutes. Adjust the slurry viscosity to approximately 3000mPa·s (25℃).

[0051] The resulting slurry had a solid content of approximately 48 wt% and a zeta potential of -41 mV.

[0052] Step 3: Drying and Finished Product Processing

[0053] This step is exactly the same as step three in Example 1, including spray drying (200°C / 90°C), airflow pulverization under nitrogen protection, passing through a 400-mesh sieve, and argon packaging.

[0054] Using the nano-copper composite negative electrode conductive agent prepared in Example 1 as a benchmark, its performance is compared with that of the traditional SP / CNT conductive agent as follows:

[0055]

[0056] The test results of this conductive agent applied to batteries are as follows:

[0057] Test battery configuration: Positive electrode: NCM811 (3.8 mAh / cm²) 2Anode: SiOx@C (420 mAh / g), with 2.0 wt% of this conductive agent added; Electrolyte: 1M LiPF6in EC:EMC (3:7) + 2% FEC; Test temperature: 25±1℃.

[0058] Fast charging performance (6C rate) test results:

[0059]

[0060] Cycle life (1C charge / 1C discharge) test results:

[0061]

[0062] Dynamic performance test results:

[0063]

[0064] Extreme environment performance test results:

[0065]

[0066] Safety performance data:

[0067]

[0068] The test results of this conductive agent compared with competing products are as follows:

[0069] Test conditions: Battery system: 3.5Ah pouch cell (NCM811 / SiOx-C anode, active material loading 3.6mAh / cm³) 2 ).

[0070] Comparison with competitors:

[0071] Competitor A: Traditional SP+CNT conductive agent (addition amount 3.0 wt%, market share >60%)

[0072] Competitor B: Graphene composite conductive agent (addition amount 2.5 wt%, a competitor in the high-end market)

[0073] This solution uses nano-copper composite conductive agent (addition amount 2.0 wt%).

[0074] The results of the core electrochemical performance comparison are as follows:

[0075]

[0076] The comparison results of safety and stability are as follows:

[0077]

[0078] The cost-efficiency comparison results are as follows:

[0079]

[0080] This invention effectively improves the fast charging capability, cycle life, and structural stability of batteries by introducing carbon-coated nano-copper and optimizing its combination with SP and CNT. Compared with high-end competitor B, it improves fast charging capability by 7.9%, reduces cost by 61%, and avoids the risk of copper leaching.

[0081] The present invention and its embodiments have been described above. This description is not restrictive, and the embodiments shown are only one of the embodiments of the present invention. The actual structure is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing carbon-coated nano-copper, characterized in that, Includes the following steps: S1: Mix the copper salt solution with glucose to obtain a mixed solution; S2: The mixed solution is subjected to a hydrothermal reaction at a temperature of 180-200℃ for 12-15 hours. S3: The product after hydrothermal reaction is centrifuged, washed, and freeze-dried to obtain the precursor; S4: The precursor is calcined under inert gas protection at a temperature of 500-550°C for 2-3 hours to obtain carbon-coated nano-copper particles. The carbon-coated copper nanoparticles have a particle size D50 of 20-50 nm and are coated with an amorphous carbon layer with a thickness of 2-5 nm.

2. The method for preparing carbon-coated nano-copper according to claim 1, characterized in that, The copper salt is CuSO4; the inert gas is nitrogen.

3. A nano-copper composite negative electrode conductive agent, characterized in that, It is composed of the following components in weight percentage: 40-50% carbon-coated copper nanoparticles; 20-30% conductive carbon black; 10-15% carbon nanotubes; 5-8% binder; 2-3% dispersant; and the balance being deionized water; wherein the carbon-coated copper nanoparticles are prepared according to the preparation method described in claim 1 or 2.

4. The nano-copper composite negative electrode conductive agent according to claim 3, characterized in that, The carbon-coated copper nanoparticles have a particle size D50 of 20-50 nm, a specific surface area of ​​30-50 m² / g, a purity of ≥99.95%, and are coated with an amorphous carbon layer with a thickness of 2-5 nm.

5. The nano-copper composite negative electrode conductive agent according to claim 3, characterized in that, The conductive carbon black has a DBP absorption value ≥400ml / 100g and a specific surface area of ​​1200-1400m² / g.

6. The nano-copper composite negative electrode conductive agent according to claim 3, characterized in that, The carbon nanotubes are carboxylated multi-walled carbon nanotubes with a diameter of 8-15 nm, a length of 5-20 μm, and a carboxyl content of 0.5-1.5 wt%.

7. The nano-copper composite negative electrode conductive agent according to claim 3, characterized in that, The binder comprises sodium carboxymethyl cellulose and styrene-butadiene rubber; the dispersant is a polyethylene glycol derivative with a molecular weight of 2000±100 Da.

8. A method for preparing a nano-copper composite conductive agent as described in any one of claims 3 to 7, characterized in that, Includes the following steps: Pre-dispersion: A portion of deionized water, dispersant, and sodium carboxymethyl cellulose from the binder are mixed and dispersed by high-speed shearing. Dispersion of nano-copper: Add the carbon-coated nano-copper particles to the mixture obtained in the previous step, and then disperse by ball milling; Dispersion of conductive materials: Add conductive carbon black and carbon nanotubes sequentially to the slurry obtained in the previous step, and then perform ultrasonic treatment; Slurry preparation: Add the remaining binder to the slurry obtained in the previous step, stir at low speed, and adjust the viscosity to 3000±500mPa·s at a temperature of 25℃ to obtain the conductive agent slurry.

9. The preparation method according to claim 8, characterized in that, The ball milling process uses zirconia balls, operates at a speed of 300 rpm, and lasts for 2 hours; the ultrasonic treatment operates at a frequency of 40 kHz, a power of 800 W, and lasts for 1 hour.

10. The preparation method according to claim 8, characterized in that, It also includes the following steps: The conductive agent slurry is spray-dried at an inlet temperature of 200°C and an outlet temperature of 90°C to obtain a dried powder. Subsequently, the dried powder is subjected to airflow pulverization and sieving under inert gas protection to obtain the finished conductive agent.

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