Graphene current collector, and preparation method therefor and use thereof

Abstract

A graphene current collector, and a preparation method therefor and the use thereof. The preparation method comprises the following steps: S1, mixing and dissolving a graphene powder, a dispersant and a polymer adhesive in a solvent, and ultrasonically stirring and dispersing same to prepare a gelatinized slurry; S2, coating a base film with the gelatinized slurry obtained in step S1, drying same, stripping off a graphene primary film, and rolling same; and S3, rolling and compacting the graphene primary film obtained in S2 to a target thickness, so as to obtain a graphene current collector. The graphene current collector replaces copper foil or aluminum foil to serve as a positive or negative electrode current collector of a lithium battery, and can significantly improve the energy density and energy efficiency of the lithium battery.

Description

A graphene current collector and its preparation method and application Technical Field

[0001] The present invention relates to the technical field of energy storage materials, and in particular to a graphene current collector and a preparation method and application thereof. Background Art

[0002] The current collector of lithium batteries is made of aluminum foil, and the current collector of the negative electrode is made of copper foil. The density of aluminum is 2.7g / cm 3 The density of copper is 8.9g / cm 3 Aluminum and copper have high densities and account for a high proportion of the mass in lithium batteries, which limits the improvement of the mass energy density of lithium batteries; the thermal conductivity of aluminum is 217W / mk, and the thermal conductivity of copper is 376W / mk. The higher the thermal conductivity, the better the thermal conduction of the battery and the safer it will be; the electrical conductivity of aluminum is 35.3S / m, and the electrical conductivity of copper is 59.6S / m. The higher the electrical conductivity, the better the battery's rate performance.

[0003] Therefore, how to develop a current collector with low density, high thermal conductivity and high electrical conductivity is the key to improving the battery mass energy density and rate performance.

[0004] CN111180741A discloses a carbon-coated current collector coated with three-dimensional graphene powder and a method for preparing the same. The preparation method involves mixing the three-dimensional graphene powder, a binder, and a dispersant in a suitable solvent, sand-milling, and sieving to produce a three-dimensional graphene powder slurry. The slurry is then evenly coated onto a substrate such as aluminum foil or copper foil to produce the carbon-coated current collector. This current collector is essentially aluminum foil or copper foil coated with a graphene coating, but still retains the inherent drawbacks of high density and low thermal and electrical conductivity.

[0005] CN115784706A discloses a method of coating a graphene slurry on a glass or polytetrafluoroethylene mold, peeling the slurry from the mold after drying to obtain a film layer, which undergoes a rapid self-expansion reduction reaction and is then rolled to obtain a self-supporting reduced graphene oxide film as a current collector. CN105489392B discloses a method of forming a porous graphene layer by aggregating porous graphene particles into a sheet-like film using carbon-based fibers and a binder. The sheet-like film is then rolled to obtain a large, connected sheet, which is then rolled to obtain a porous graphene layer.

[0006] However, the above existing technologies have the problems of being difficult to continuously produce in batches at low cost and being only suitable for laboratories, and thus need further improvement. Technical issues

[0007] To solve the problems existing in the prior art, the present invention provides a graphene current collector and a preparation method thereof, which can greatly improve the capacity density, safety performance, power density and service life of lithium batteries.

[0008] Another object of the present invention is to provide applications of the graphene current collector. Technical Solutions

[0009] In order to achieve the above object of the invention, the present invention adopts the following technical solutions:

[0010] A method for preparing a graphene current collector comprises the following steps:

[0011] S1, dissolving graphene powder, dispersant and polymer adhesive in a solvent, and dispersing them by ultrasonic stirring to prepare a gel slurry;

[0012] S2, coating the gelled slurry in S1 on the base film, drying it, peeling off the primary graphene film, and rolling it up;

[0013] S3. Roll-press and compact the graphene film obtained in S2 to a target thickness to obtain a graphene current collector.

[0014] In a specific embodiment, the graphene powder is prepared by a mechanical exfoliation method or a chemical exfoliation method; preferably, the graphene powder is single-layer graphene or multi-layer graphene.

[0015] In a specific embodiment, the dispersant in S1 is at least one of a silane coupling agent, sodium dodecylsulfonate, sodium dodecylbenzenesulfonate, polyvinyl alcohol, sodium ligninsulfonate, hexadecyltrimethylammonium bromide, and polyvinylpyrrolidone;

[0016] In a specific embodiment, the polymer binder in S1 is at least one of SBR, PTFE, PVDF, PI, and PLA;

[0017] In a specific embodiment, the solvent in S1 is water or an organic solvent. Preferably, the organic solvent is selected from at least one of methanol, ethanol, isopropanol, DMSO, DMF, and NMP.

[0018] In a specific embodiment, the mass ratio of graphene powder, dispersant and polymer binder in S1 is 60%-98%: 1%-10%: 1%-30%.

[0019] In a specific embodiment, the ultrasonic power in S1 is 100 to 1000 W / Kg;

[0020] In a specific embodiment, the linear speed of the stirring and dispersing in S1 is 10 to 30 m / s;

[0021] In a specific embodiment, the ultrasonic stirring and dispersion time in S1 is 2 to 48 hours;

[0022] In a specific embodiment, the solid content of the gelled slurry prepared in S1 is 2 wt % to 80 wt %.

[0023] In a specific embodiment, the coating in S2 is selected from any one of extrusion coating, slurry coating, and micro-gravure coating;

[0024] In a specific embodiment, the base membrane in S2 is selected from any one of stainless steel membrane, plastic film, non-woven fabric, and polysulfone membrane.

[0025] In a specific embodiment, the surface density of the graphene film in S2 is 2 to 48 g / m 2 ;.

[0026] In a specific embodiment, the target thickness of the compaction in S3 is 5 to 30 μm;

[0027] Preferably, the compacted density is 0.4 to 1.6 g / cm 3 .

[0028] On the other hand, the graphene current collector prepared by the above preparation method.

[0029] On the other hand, the graphene current collector prepared by the aforementioned preparation method or the application of the aforementioned graphene current collector in energy storage batteries, especially as positive and negative current collectors of lithium batteries. Beneficial effects

[0030] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0031] The present invention is a novel graphene current collector, which uses graphene film as the positive and negative current collector of lithium batteries. The graphene film of the present invention has a low density of only 0.4-1.6g / cm 3 , used as a current collector, can greatly reduce the weight ratio of the current collector and significantly improve the energy density of the lithium battery; the graphene film of the present invention has high thermal conductivity, with a thermal conductivity coefficient exceeding 600W / mk, which greatly improves the thermal balance and safety performance of the battery; the electrical conductivity of the graphene film of the present invention exceeds 100S / m, which effectively improves the internal resistance of the battery.

[0032] Based on the above performance advantages, the graphene film of the present invention can be used as a current collector for lithium batteries to significantly improve the capacity density, safety performance, power density and service life of lithium batteries. Best Mode for Carrying Out the Invention

[0033] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] A method for preparing a graphene current collector, comprising the following specific steps:

[0035] S1, dissolving graphene powder, dispersant and polymer adhesive in a solvent, and dispersing them by ultrasonic stirring to prepare a gel slurry;

[0036] S2, coating the gelled slurry in S1 on the base film using a coating process, peeling off the primary graphene film after drying, and rolling it up;

[0037] S3. Roll-press the S2 graphene primary film to a set thickness to obtain a graphene current collector.

[0038] The graphene current collector of the present invention can replace the existing aluminum foil and copper foil current collectors to be assembled into a lithium ion battery.

[0039] In the present invention, the graphene powder in S1 can be obtained by mechanical exfoliation or chemical exfoliation. There is no special limitation on the preparation method. It can be prepared by referring to the preparation method of the prior art, or the finished graphene product can be purchased directly from the market. The particle size of the graphene is, for example, 100-500 nm, preferably 300-500 nm. The graphene powder in S1 should have a relatively complete structure and maintain the conductive properties of the graphene body. The graphene powder can be a single layer, a single or a few layers, or a multilayer according to the performance requirements.

[0040] The dispersant in S1 is one or a combination of two or more of silane coupling agent, sodium dodecylsulfonate, sodium dodecylbenzenesulfonate, polyvinyl alcohol, sodium ligninsulfonate, hexadecyltrimethylammonium bromide, polyvinylpyrrolidone, etc., preferably a silane coupling agent.

[0041] The polymer adhesive in S1 is one or a combination of two or more of styrene-butadiene rubber (SBR), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyimide (PI), polylactic acid (PLA), etc., preferably PVDF.

[0042] The mass ratio of graphene powder, dispersant and polymer adhesive in S1 of the present invention is 60%-98%: 1%-10%: 1%-30%; for example, any ratio of (60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%): (1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%): (1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 15%, 18%, 20%, 23%, 25%, 28%, 30%).

[0043] In the present invention, the solvent in S1 can be water or an organic solvent, and the organic solvent includes one or a combination of two or more of methanol, ethanol, isopropanol, DMSO, DMF, NMP, etc., for example, NMP; the amount of solvent added is based on the solid content of the slurry prepared in step S1 being 2% to 80%, for example, the solid content is 2wt%, 5wt%, 10wt%, 20wt%, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, 80wt%, etc.

[0044] In the present invention, the ultrasonic power in S1 corresponds to 100-1000 W / Kg, that is, based on the unit mass (Kg) of all raw materials, the ultrasonic power corresponds to 100-1000 W / Kg, for example, 100 W / Kg, 200 W / Kg, 300 W / Kg, 400 W / Kg, 500 W / Kg, 600 W / Kg, 700 W / Kg, 800 W / Kg, 900 W / Kg, 1000 W / Kg, etc. The stirring and dispersing linear velocity is 10 to 30 m / s, for example, 10 m / s, 13 m / s, 15 m / s, 18 m / s, 20 m / s, 23 m / s, 25 m / s, 28 m / s, 30 m / s, etc.; the ultrasonic stirring and dispersing time is 2 to 48 h, for example, 2 h, 5 h, 10 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 45 h, 48 h, etc.

[0045] In the present invention, the coating method in S2 can be various coating methods such as extrusion coating, slurry coating, micro-gravure coating, etc., without special restrictions, for example, coating is performed using an extrusion coater.

[0046] The base membrane in S2 can be a stainless steel membrane, a plastic film, a non-woven fabric, etc., or other base membranes such as a polysulfone membrane.

[0047] The surface density of the graphene film in S2 is 2 to 48 g / m 2 , for example 2g / m 2 , 5g / m 2 , 10g / m 2 , 15g / m 2 , 20g / m 2, 25g / m 2 , 30g / m 2 , 35g / m 2 , 40g / m 2 , 48g / m 2 wait.

[0048] In the present invention, the compacted density of S3 is 0.4 to 1.6 g / cm 3 , for example 0.4g / cm 3 , 0.6g / cm 3 , 0.8g / cm 3 , 1g / cm 3 , 1.2g / cm 3 , 1.4g / cm 3 , 1.6g / cm 3 wait.

[0049] The compacted thickness in S3 is 5 to 30 μm, for example, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, etc., preferably 15-30 μm.

[0050] The graphene current collector of the present invention is used as a positive electrode current collector. With the same thickness, the weight ratio of the current collector can be reduced by 40-85%.

[0051] The graphene current collector of the present invention is used as a negative electrode current collector. With the same thickness, the weight ratio of the current collector can be reduced by 82-95%.

[0052] When the graphene current collector of the present invention replaces the copper foil or aluminum foil current collector for assembly and lead-out, a conductive adhesive is used as a force and electrical connection method.

[0053] The present invention is further explained below by more specific examples, but does not constitute any limitation.

[0054] Main ingredients:

[0055] Graphene (using SE1232 graphene powder from Changzhou Sixth Element Materials Technology Co., Ltd.).

[0056] In the present invention, other raw materials not specifically described are conventional raw materials and can be directly purchased from the market and used. Performance testing method:

[0057] Prepare 2714891 square battery cells and test their energy density and energy efficiency.

[0058] Refer to GB / T 36276-2018 Lithium-ion batteries for power energy storage

[0059] The energy density of a battery cell is calculated by calibrating the discharge energy of the battery cell at 1P power and dividing it by the mass of the battery cell. For example, if the discharge energy of a battery cell is calibrated to 64Wh using a 64W discharge power and the cell mass is 700g, then the energy density of the battery cell is 91.43Wh / Kg.

[0060] Energy efficiency is the ratio of charge and discharge energy. For example, if the energy of a battery cell is 64Wh, then the 1P power is 64W and the 4P power is 256W. The 4P energy efficiency is calculated by charging and discharging at 4P power, and the discharge energy divided by the charging energy is the 4P energy efficiency. Example 1

[0061] 1) Add 0.5 kg PVDF to 20 kg NMP solvent and stir for 5 hours to dissolve PVDF in NMP;

[0062] 2) Add 0.3 kg of silane coupling agent as a dispersant to the solution from the previous step, and then add 9.2 kg of the oligolayer redox graphene powder. Use ultrasonic stirring equipment to stir and disperse. Set the ultrasonic power to 1000 W / kg and the stirring linear speed to 25 m / s. Ultrasonic stirring and dispersion are performed for 8 hours to obtain a slurry with a fineness of less than 20 μm.

[0063] 3) Use the extrusion coater to coat the slurry in the previous step, and set the coating surface density to 8g / m 2 The coating base film is a stainless steel film, and the baking temperature is 70°C. After baking, the graphene primary film is peeled off on the stainless steel base film;

[0064] 4) The graphene film was rolled by a roller press with a thickness of 10 μm and a compaction density of 0.8 g / cm 3 ;

[0065] 5) Use the graphene film from the previous step as the positive and negative current collectors of the lithium battery. The positive electrode active material uses lithium iron phosphate, and the surface density of the coating auxiliary material is 180g / m 2 The compaction density of the auxiliary material after roller pressing is 2.2g / cm 3 The electrode thickness is 92μm; the negative electrode active material is artificial graphite, and the surface density of the coating auxiliary material is 100g / m 2 The compaction density of the auxiliary material after roller pressing is 1.4 g / cm 3 , the electrode thickness is 81 μm;

[0066] 6) Assemble the above positive and negative electrodes into a square 2714891 lithium battery. Example 2

[0067] 1) Add 1.5 kg of SBR to 40 kg of DMF solvent and stir for 5 hours to dissolve the SBR in DMF;

[0068] 2) Add 0.8 kg of silane coupling agent as a dispersant to the solution from the previous step, and then add 9.2 kg of the oligolayer redox graphene powder. Use ultrasonic stirring equipment to stir and disperse. Set the ultrasonic power to 500 W / kg and the stirring linear speed to 8 m / s. Ultrasonic stirring and dispersion are performed for 45 hours to obtain a slurry with a fineness of less than 20 μm.

[0069] 3) Use the extrusion coater to coat the slurry in the previous step, and set the coating surface density to 8g / m 2 The coating base film is a stainless steel film, and the baking temperature is 60°C. After baking, the graphene primary film is peeled off from the stainless steel base film;

[0070] 4) The graphene film was rolled by a roller press to a thickness of 6 μm and a compaction density of 1.33 g / cm 3 ;

[0071] 5) Use the graphene film from the previous step as the positive and negative current collectors of the lithium battery. The positive electrode active material uses lithium iron phosphate, and the surface density of the coating auxiliary material is 180g / m 2 The compaction density of the auxiliary material after roller pressing is 2.2g / cm 3 The electrode thickness is 88μm; the negative electrode active material is artificial graphite, and the surface density of the coating auxiliary material is 100g / m 2 The compaction density of the auxiliary material after roller pressing is 1.4 g / cm 3 , the electrode thickness is 77 μm;

[0072] 6) Assemble the above positive and negative electrodes into a square 2714891 lithium battery. Example 3

[0073] 1) Add 1.2 kg of PI to 80 kg of DMSO solvent and stir for 5 hours to dissolve the PI in DMSO;

[0074] 2) Add 0.6 kg of silane coupling agent as a dispersant to the solution from the previous step, and then add 9.2 kg of the oligolayer redox graphene powder. Use ultrasonic stirring equipment to stir and disperse. Set the ultrasonic power to 100 W / kg and the stirring linear speed to 30 m / s. Ultrasonic stirring and dispersion are performed for 4 hours to obtain a slurry with a fineness of less than 20 μm.

[0075] 3) Use the extrusion coater to coat the slurry in the previous step, and set the coating surface density to 13g / m 2 The coating base film is a stainless steel film, and the baking temperature is 80°C. After baking, the graphene primary film is peeled off from the stainless steel base film;

[0076] 4) The graphene film was rolled by a roller press with a thickness of 10 μm and a compaction density of 1.3 g / cm 3 ;

[0077] 5) Use the graphene film from the previous step as the positive and negative current collectors of the lithium battery. The positive electrode active material uses lithium iron phosphate, and the surface density of the coating auxiliary material is 180g / m 2 The compaction density of the auxiliary material after roller pressing is 2.2g / cm 3 The electrode thickness is 92μm; the negative electrode active material is artificial graphite, and the surface density of the coating auxiliary material is 100g / m 2 The compaction density of the auxiliary material after roller pressing is 1.4 g / cm 3 , the electrode thickness is 81 μm;

[0078] 6) Assemble the above positive and negative electrodes into a square 2714891 lithium battery. Comparative Example 1

[0079] Aluminum foil is used as the positive electrode current collector. The thickness of the aluminum foil is 13 μm and the surface density of the aluminum foil is 35.1 g / m 2 The positive electrode active material is lithium iron phosphate, and the surface density of the coating auxiliary material is 180g / m 2 The compaction density of the auxiliary material after roller pressing is 2.2g / cm 3 , the electrode thickness is 95μm;

[0080] Copper foil is used as the negative electrode current collector. The thickness of the copper foil is 8 μm and the surface density of the copper foil is 71.2 g / m 2 ; The negative electrode active material is artificial graphite, and the surface density of the coating auxiliary material is 100g / m 2 The compaction density of the auxiliary material after roller pressing is 1.4 g / cm 3 , the electrode thickness is 79μm;

[0081] The above positive and negative electrodes are assembled into a square 2714891 lithium battery. <Performance Test>

[0082] The square 2714891 lithium battery was assembled with the current collectors of the embodiment and the comparative example, and the battery performance test was performed. The test results are shown in Table 1.

[0083] Table 1 Performance test data of examples and comparative examples

[0084] ,

[0085] As can be seen from the above table, the graphene current collector of the present invention can significantly increase the energy density and energy efficiency of lithium batteries.

[0086] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A preparation method of a graphene current collector, characterized in that, It includes the following steps: S1. Mix graphene powder, a dispersant and a polymer binder and dissolve them in a solvent, and stir and disperse them by ultrasonic waves to prepare a gelled slurry; S2. Coat the gelled slurry in S1 on a base film, dry it and then peel off the initial graphene film, and wind it up; S3. Roll and compact the initial graphene film obtained in S2 to a target thickness to obtain a graphene current collector.

2. The preparation method according to claim 1, characterized in that, The graphene powder is prepared by a mechanical exfoliation method or a chemical exfoliation method; preferably, the graphene powder is monolayer graphene or multilayer graphene.

3. The preparation method according to claim 1 or 2, characterized in that, The dispersant in S1 is at least one of silane coupling agent, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, polyvinyl alcohol, sodium lignosulfonate, cetyltrimethylammonium bromide, polyvinylpyrrolidone; and / or The polymer binder in S1 is at least one of SBR, PTFE, PVDF, PI, PLA; and / or The solvent in S1 is water or an organic solvent, preferably, the organic solvent is selected from at least one of methanol, ethanol, isopropanol, DMSO, DMF, NMP.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The mass ratio of the graphene powder, the dispersant and the polymer binder in S1 is 60% - 98%: 1% - 10%: 1% - 30%.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The ultrasonic power in S1 is 100 - 1000 W / Kg; and / or The linear velocity of stirring and dispersing in S1 is 10 - 30 m / s; and / or The time of ultrasonic stirring and dispersing in S1 is 2 - 48 h; and / or The solid content of the gelled slurry prepared in S1 is 2 wt% - 80 wt%.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The coating in S2 is selected from any one of extrusion coating, doctor blade coating, microgravure coating; and / or The base film in S2 is selected from any one of stainless steel film, plastic film, non-woven fabric, polysulfone film.

7. The preparation method according to claim 6, characterized in that, The areal density of the initial graphene film in S2 is 2 to 48 g / m 2 ;.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The target thickness of compaction in S3 is 5 - 30 μm; Preferably, the compaction density is 0.4 to 1.6 g / cm 3 .

9. A graphene current collector prepared by the preparation method according to any one of claims 1 - 8.

10. Application of the graphene current collector prepared by the preparation method according to any one of claims 1 - 8 or the graphene current collector according to claim 9 in an energy storage battery, especially as a positive and negative current collector of a lithium battery.

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