Graphene carbon nanotube lithium ion battery and preparation method thereof

Abstract

The application provides a graphene carbon nanotube lithium ion battery, which comprises a battery shell, an electrode group and an electrolyte sealed in the battery shell, the electrode group comprises a positive electrode material, a negative electrode material and a diaphragm between the positive electrode and the negative electrode; the positive electrode material comprises a current collector and a conductive coating coated on the current collector; the conductive coating is obtained by coating and curing of a conductive slurry. The application provides a lithium ion battery with good electrochemical performance.

Description

TECHNICAL FIELD

[0001] The application relates to the field of batteries, in particular to a graphene carbon nanotube lithium ion battery and a preparation method thereof. BACKGROUND

[0002] In the material system currently used in lithium ion batteries, the negative electrode material is mostly fixed, and the change of the positive electrode material determines the pros and cons of the power battery. The existing positive electrode material active substance has poor conductivity, and the internal resistance between electrodes is large, so that the active substance cannot be fully reacted. The traditional conductive agent cannot meet the current demand due to the excessively low rate and capacity, and the development of a new type of conductive agent combined with high-capacity ternary materials to prepare a battery with high performance, large capacity and long service life is a hot research topic at present. Innovating battery materials is a key link in the progress of lithium ion battery preparation technology, and developing new positive electrode materials in combination with the use requirements of batteries to improve the performance of lithium batteries is a major direction for promoting the development of the lithium ion battery industry.

[0003] Slurry preparation is an important step in battery production, which mainly realizes the purpose of fully mixing active material and non-active components. Therefore, the preparation and performance of electrode slurry directly affect the electrochemical performance of electrode sheets. In order to ensure that the electrode sheet fully exhibits its electrochemical characteristics, on the one hand, the uniformity of the slurry is ensured to ensure the uniform mixing of each component, avoid agglomeration, and also ensure the controllability of the electrode sheet loading capacity and the true repeatability of the electrochemical performance; on the other hand, the matching of non-active components and active substances, the selection of conductive agents with excellent conductivity and adhesion systems with excellent adhesion performance can reduce the content of non-active components while improving the electrochemical performance, and improve the overall energy density of the battery.

[0004] In the working process of lithium ion batteries, there is not only the migration of positive and negative ions, but also the transmission of electrons. However, the ion and electron conductivity of the active material coated on the positive and negative electrodes is not high, and the electrical conductivity of the positive electrode material is generally 10 -1 ~ 10 -6 S / cm, which is relatively low for the transmission rate of electrons in the whole system, so the performance of the battery under high-rate current is not high. Therefore, in order to improve the migration rate of ions and electrons, an appropriate amount of conductive agent is often added to the positive and negative electrodes, so as to effectively reduce the internal resistance of the battery and build a high-speed electron transmission track. SUMMARY

[0005] The application improves the conductive slurry by adding an appropriate amount of conductive agent and active substance to the positive electrode, thereby effectively reducing the internal resistance of the battery, building a high-speed electron transmission track, and further improving the electrochemical performance of the battery.

[0006] The graphene carbon nanotube lithium ion battery comprises a battery shell and an electrode group and an electrolyte sealed in the battery shell, and the electrode group comprises a positive electrode material, a negative electrode material and a separator between the positive electrode and the negative electrode.

[0007] The positive electrode material comprises a current collector and a conductive coating coated on the current collector; the conductive coating is obtained by coating and curing a conductive slurry.

[0008] The conductive slurry is composed of active substance, organic bentonite, polyacrylic acid, carboxymethyl cellulose and conductive agent in a mass ratio of 70-97.5%, 0.1-5%, 0.5-15%, 0.5-10% and 1-5% respectively; wherein the conductive agent is composed of carbon nanotubes, graphene and super-conductive carbon black in a mass ratio of 0.5-1.5, 0.5-1.5 and 1-2 respectively. The active substance is composed of LiNi 0.8 Co 0.15 Al 0.05 O2 and LiMn2O4 in a mass ratio of 1.7-8:1. The particle size of the graphene is 50-400 nm, and the carbon nanotube diameter is 5-10 nm. The thickness of the conductive coating is 0.1-4 microns.

[0009] The graphene carbon nanotube lithium ion battery comprises a battery shell and an electrode group and an electrolyte sealed in the battery shell, and the electrode group comprises a positive electrode material, a negative electrode material and a separator between the positive electrode and the negative electrode.

[0010] First, the positive electrode material is prepared, then the prepared positive electrode material is put into the battery shell, the electrolyte and the negative electrode material are added, and finally the battery shell is covered and packaged to obtain the graphene carbon nanotube lithium ion battery.

[0011] The beneficial effects obtained by the present application include at least one of the following:

[0012] 1. The graphene carbon nanotube lithium ion battery prepared by the present application effectively combines and utilizes the advantages of graphene and carbon nanotubes, and improves the electrochemical performance by mixing conductive agent and active substance. The graphene carbon nanotube lithium ion battery prepared by the present application has good cycle stability while improving the capacity.

[0013] 2. The graphene carbon nanotube lithium ion battery prepared by the present application has good conductivity, for example, the initial specific discharge capacity is not less than 150 mAh / g. The graphene carbon nanotube lithium ion battery prepared by the present application has good cycle performance, for example, the cycle performance is not less than 105 mAh / g at 0.2C for 200 times. DETAILED DESCRIPTION

[0014] In one exemplary embodiment of the present application, a graphene carbon nanotube lithium ion battery includes a battery housing and an electrode group and an electrolyte sealed in the battery housing, the electrode group including a positive electrode material, a negative electrode material, and a separator between the positive electrode and the negative electrode.

[0015] The separator can be a polypropylene separator, a polyethylene separator, and a polypropylene and polyethylene composite film. The electrolyte is 0.8-1.2 mol / L LiPF6 / EC+DMC+DEC+EMC. For example, 1 mol / L LiPF6 electrolyte is configured using a mixed solvent system of EC+DMC+DEC+EMC in a volume ratio of 1:1:1:1. However, the present application is not limited thereto. The thickness of the current collector is 8-10 μm.

[0016] The negative electrode material can include a copper foil and a conductive coating coated on the copper foil; the conductive coating is obtained by coating and curing a conductive paste; the conductive paste is composed of active material: binder in a mass ratio of 8-10:1, the binder is composed of butadiene-styrene rubber and sodium carboxymethyl cellulose in a mass ratio of 0.2-2:1; the active material is a graphite material. However, the present application is not limited thereto.

[0017] The positive electrode material includes a current collector and a conductive coating coated on the current collector; the conductive coating is obtained by coating and curing a conductive paste.

[0018] The conductive paste of the positive electrode material is composed of active material: organic bentonite: polyacrylic acid: carboxymethyl cellulose: conductive agent in a mass ratio of 70-97.5%:0.1-5%:0.5-15%:0.5-10%:1-5%; wherein the conductive agent is composed of carbon nanotube: graphene: super-conductive carbon black in a mass ratio of 0.5-1.5:0.5-1.5:1-2.

[0019] The active material is LiNi 0.8 Co 0.15 Al 0.05 O2 and LiMn2O4 in a mass ratio of 1.7-8:1; the particle size of the graphene is 50-400 nm, the carbon nanotube diameter is 5-10 nm; the thickness of the conductive coating is 0.1-4 μm.

[0020] The current collector can be a copper foil or an aluminum foil, and the solvent of the conductive paste can be at least one of deionized water, anhydrous ethanol, and an alkaline solution.

[0021] In one exemplary embodiment of the present application, the active material: organic bentonite: polyacrylic acid: carboxymethyl cellulose: conductive agent is in a mass ratio of 75-90%:1.5-4%:3-10%:2-8%:2-4%.

[0022] In one exemplary embodiment of the present application, the mass ratio of the active material: organic bentonite: polyacrylic acid: carboxymethyl cellulose: conductive agent is 80-85%: 2-3%: 5-8%: 4-6%: 2.5-3%.

[0023] In one exemplary embodiment of the present application, the mass ratio of the carbon nanotube: graphene: super-conductive carbon black is 0.8-1.2: 0.8-1.2: 1.2-1.6. The particle size of the graphene is 100-300 nm, and the carbon nanotube diameter is 7-9 nm.

[0024] In one exemplary embodiment of the present application, the preparation method of the graphene carbon nanotube lithium ion battery comprises the following steps:

[0025] 1) Preparation of the positive electrode material: mix the organic bentonite, polyacrylic acid and carboxymethyl cellulose, and drop deionized water to fully dissolve, to obtain a first mixture. Add the conductive agent to the first mixture and stir uniformly to obtain a second mixture. Further stir the second mixture to add the active material, to obtain the graphene carbon nanotube composite conductive slurry. Uniformly coat the conductive slurry on the current collector, and after drying, perform tabletting to obtain the positive electrode material.

[0026] 2) Preparation of the lithium ion battery: place the positive electrode material prepared in step 1) into the battery shell, add the electrolyte and the negative electrode material, and finally cover the battery shell to perform packaging to obtain the lithium ion battery.

[0027] The specific preparation steps of the graphene carbon nanotube lithium ion battery of the present application are as follows:

[0028] Example 1

[0029] Grind the active material, carbon nanotube, graphene and super-conductive carbon black required for the experiment. The grinding can be performed using a mortar. The raw materials are in a mass ratio of 2%: 3%: 3% of organic bentonite: polyacrylic acid: carboxymethyl cellulose. Drop deionized water, perform magnetic constant-temperature stirring, and after fully dissolving, add the conductive agent and stir uniformly. The mass ratio of the carbon nanotube: graphene: super-conductive carbon black is 0.8: 0.8: 1. The particle size of the graphene is 100 nm, and the carbon nanotube diameter is 6 nm. Finally, add the active material and further stir. The mass ratio of the active materials LiNi 0.8 Co 0.15 Al 0.05 O2 and LiMn2O4 is 2:1, to obtain the graphene carbon nanotube composite conductive slurry. Coat the conductive slurry on the aluminum foil. The conductive slurry can be uniformly coated on the aluminum foil using a coating machine spatula. After coating, place in a vacuum drying oven, dry at 100°C for 8h, and then perform tabletting to obtain the graphene carbon nanotube positive electrode material. The conductive coating thickness is 2.5 pm.

[0030] The preparation method of the negative material comprises the following specific steps: mixing a binder, styrene-butadiene rubber, and sodium carboxymethyl cellulose according to a mass ratio of 1:1, adding deionized water to stir, then adding graphite according to a mass ratio of active substance: binder 9:1 to further stir uniformly to obtain a conductive slurry of the negative electrode, coating the conductive slurry on a 9 μm thick copper foil, drying, and then pressing to obtain the negative material.

[0031] The lithium ion battery is assembled in a vacuum drying box, and the specific steps are as follows: the prepared positive material is put into a battery shell, 1 mol / L LiPF6 electrolyte configured by a mixed solvent system of polypropylene separator and EC+DMC+DEC+EMC in a volume ratio of 1:1:1:1 is added, the negative material is added, the battery shell is covered, and the lithium ion battery is sealed well on a sealing machine with a pressure of 5 MPa.

[0032] Example 2

[0033] The active substance, carbon nanotubes, graphene and super-conductive carbon black required for the experiment are ground, the raw materials are added dropwise with deionized water, and the mixture is stirred at a constant temperature by a magnetic force, and after being fully dissolved, the conductive agent is added and stirred uniformly, wherein the mass ratio of carbon nanotubes: graphene: super-conductive carbon black is 1:0.8:1.5, the particle size of graphene is 80 nm, the diameter of carbon nanotubes is 9 nm, and finally the active substance is added and further stirred, wherein the mass ratio of LiNi 0.8 Co 0.15 Al 0.05 O2 and LiMn2O4 is 5:1 to obtain the graphene carbon nanotube composite conductive slurry. The conductive slurry is coated on an aluminum foil, and the conductive slurry is uniformly coated on the aluminum foil using a coating machine spatula. After coating, it is placed in a vacuum drying oven at 80°C for 12 hours, and then pressed to obtain the graphene carbon nanotube positive material, and the thickness of the conductive coating is 2.5 μm.

[0034] The preparation method of the negative material comprises the following specific steps: mixing a binder, styrene-butadiene rubber, and sodium carboxymethyl cellulose according to a mass ratio of 1:1, adding deionized water to stir, then adding graphite according to a mass ratio of active substance: binder 9:1 to further stir uniformly to obtain a conductive slurry of the negative electrode, coating the conductive slurry on a 9 μm thick copper foil, drying, and then pressing to obtain the negative material.

[0035] Assembled into lithium ion battery in vacuum drying oven, the specific steps are: the prepared positive electrode material is put into the battery shell, 0.9mol / L LiPF6 electrolyte of EC+DMC+DEC+EMC volume ratio 1:1:1:1 mixed solvent system is added, the negative electrode material is added, the battery shell is covered, and the lithium ion battery is sealed on the sealing machine with a pressure of 5MPa.

[0036] Example 3

[0037] The active substance, carbon nanotube, graphene and super conductive carbon black required for the experiment are ground in a mortar. The raw materials are added dropwise with deionized water in a mass ratio of 2%:10%:6% of organic bentonite: polyacrylic acid: carboxymethyl cellulose. Magnetic constant temperature stirring is carried out, and after sufficient dissolution, the conductive agent is added and stirred uniformly. The mass ratio of carbon nanotube: graphene: super conductive carbon black is 0.8:1:1.5. The particle size of graphene is 200nm, and the carbon nanotube diameter is 6nm. Finally, the active substance LiNi 0.8 Co 0.15 Al 0.05 O2 and LiMn2O4 are 5:1, to obtain the graphene carbon nanotube composite conductive paste. The conductive paste is coated on the aluminum foil, and the conductive paste is uniformly coated on the aluminum foil using a coating machine spatula. After coating, it is placed in a vacuum drying oven at 80℃ for 12h, and then pressed to obtain the graphene carbon nanotube positive electrode material. The thickness of the conductive coating is 3.5μm.

[0038] The specific steps of the preparation method of the negative electrode material are as follows: the binder styrene-butadiene rubber and carboxymethyl cellulose sodium are mixed in a mass ratio of 1:1, deionized water is added for stirring, then the active substance is added in a mass ratio of 9:1, and the graphite is further stirred uniformly to obtain the conductive paste of the negative electrode. The conductive paste is coated on the 9μm thick copper foil, dried, and then pressed to obtain the negative electrode material.

[0039] Assembled into lithium ion battery in vacuum drying oven, the specific steps are: the prepared positive electrode material is put into the battery shell, 0.9mol / L LiPF6 electrolyte of EC+DMC+DEC+EMC volume ratio 1:1:1:1 mixed solvent system is added, the negative electrode material is added, the battery shell is covered, and the lithium ion battery is sealed on the sealing machine with a pressure of 5MPa.

[0040] Comparative Example 1

[0041] Based on Example 1, the difference is that no organic bentonite is added in the conductive paste.

[0042] Comparative Example 2

[0043] On the basis of Example 1, the difference is that no polyacrylic acid is added in the conductive paste.

[0044] Comparative Example 3

[0045] On the basis of Example 1, the difference is that no carboxymethyl cellulose is added in the conductive paste.

[0046] Comparative Example 4

[0047] On the basis of Example 1, the difference is that no super-conductive carbon black is added.

[0048] Comparative Example 5

[0049] On the basis of Example 1, the difference is that no carbon nanotube is added.

[0050] Comparative Example 6

[0051] On the basis of Example 1, the difference is that no graphene is added.

[0052] At 25℃, the lithium ion batteries of Examples 1 to 3 and Comparative Examples 1 to 6 are respectively subjected to electrochemical performance, cycle performance and AC impedance tests under the same environment. The results are shown in Table 1.

[0053] Table 1

[0054]

[0055] Referring to Table 1, the first discharge specific capacity of the lithium ion battery prepared by the present application at 0.1C rate is not less than 150mAh / g. Comparative Example 4, Comparative Example 5 and Comparative Example 6 are compared with Example 1 respectively, and it can be seen that the first discharge specific capacity of the battery at 0.1C rate is improved by adding carbon nanotube, graphene and super-conductive carbon black in the conductive paste. Comparative Example 1, Comparative Example 2 and Comparative Example 3 are compared with Example 1 respectively, and it can be seen that the change of dispersant in the conductive paste has no obvious effect on the discharge specific capacity of the battery.

[0056] As shown in Table 1, referring to Example 1, Example 2 and Example 3, it can be seen that the lithium ion battery prepared by the present application has good cycle performance, and the discharge specific capacity is not less than 105mAh / g after 200 cycles at 0.2C and 3-4.2V. Comparative Example 4, Comparative Example 5 and Comparative Example 6 are compared with Example 1 respectively, and it can be seen that the cycle performance of the battery is obviously improved by adding carbon nanotube, graphene and super-conductive carbon black in the conductive paste, and the improvement is more than 20mAh / g. Comparative Example 1, Comparative Example 2 and Comparative Example 3 are compared with Example 1 respectively, and it can be seen that the combination of the three dispersants is beneficial to improve the cycle performance of the battery. In addition, under the condition that other conditions are equivalent, referring to Example 1, Example 2 and Example 3, the active material LiNi 0.8 Co0.15 Al 0.05 The higher the O2 content, the better the battery cycle performance.

[0057] As shown in Table 1, the comparative example 4, the comparative example 5 and the comparative example 6 are compared with the example 1 respectively, and it can be seen that the conductive paste with the carbon nanotube, the graphene and the super conductive carbon black added simultaneously has low battery internal resistance.

[0058] In summary, the graphene carbon nanotube lithium ion battery prepared by the application effectively combines and utilizes the advantages of the graphene and the carbon nanotube, and the electrochemical performance is improved by mixing the conductive agent and the active material, the graphene carbon nanotube lithium ion battery improves the capacity while having good cycle stability, for example, the initial discharge specific capacity is not less than 150 mAh / g. The graphene carbon nanotube lithium ion battery prepared by the application has good cycle performance, for example, the cycle performance is not less than 105 mAh / g at 0.2C after 200 times.

[0059] The above only describes the embodiments of the application and is not intended to limit the application. The application can be variously changed and modified by those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the application shall be included in the scope of the claims of the application.

Claims

1. A graphene carbon nanotube lithium ion battery, characterized in that, The diaphragm is a polypropylene diaphragm and / or a polyethylene diaphragm, the electrolyte is 0.8-1.2 mol / L LiPF6 / EC+DMC+DEC+EMC; the thickness of the current collector is 8-10 microns; Battery shell and electrode group and electrolyte sealed in the battery shell, the electrode group includes positive electrode material, negative electrode material and diaphragm between the positive electrode material and the negative electrode material;The positive electrode material includes current collector and conductive coating coated on the current collector;The conductive coating is obtained by coating and curing conductive paste;The conductive paste is composed of the following components: active substance: organic bentonite: polyacrylic acid: carboxymethyl cellulose: conductive agent mass ratio is 70-97.5%: 0.1-5%: 0.5-15%: 0.5-10%: 1-5%;Wherein the conductive agent is composed of carbon nanotube: graphene: super conductive carbon black according to the mass ratio of 0.5-1.5: 0.5-1.5: 1-2;The active substance is composed of LiNi 0.8 Co 0.15 Al 0.05 O2 and LiMn2O4 according to the mass ratio of 1.7-8: 1;The particle size of the graphene is 50-400nm, and the carbon nanotube diameter is 5-10nm;The thickness of the conductive coating is 0.1-4μm; The negative electrode material comprises a copper foil and a conductive coating coated on the copper foil; the conductive coating is obtained by coating and curing of a conductive paste; the conductive paste is composed of active substance: binder in a mass ratio of 8-10:1, the binder is composed of butadiene-styrene rubber and sodium carboxymethyl cellulose in a mass ratio of 0.2-2:1; the active substance is a graphite material; The solvent of the conductive paste is at least one of deionized water, anhydrous ethanol and an alkaline solution. The mass ratio of the active substance: organic bentonite: polyacrylic acid: carboxymethyl cellulose: conductive agent is 75-90%: 1.5-4%: 3-10%: 2-8%: 2-4%.

2. The graphene carbon nanotube lithium-ion battery of claim 1, wherein, The mass ratio of the active substance: organic bentonite: polyacrylic acid: carboxymethyl cellulose: conductive agent is 80-85%: 2-3%: 5-8%: 4-6%: 2.5-3%.

3. The graphene carbon nanotube lithium-ion battery of claim 1, wherein, The mass ratio of the carbon nanotube: graphene: super-conductive carbon black is 0.8-1.2: 0.8-1.2: 1.2-1.

6.

4. The graphene carbon nanotube lithium-ion battery of claim 1, wherein, The particle size of the graphene is 100-300 nm, and the carbon nanotube tube diameter is 7-9 nm.

5. The graphene carbon nanotube lithium-ion battery of claim 1, wherein, The method comprises the following steps:

6. A method of producing a graphene carbon nanotube lithium ion battery as claimed in any one of claims 1 to 5, characterized by, First, the preparation of the positive electrode material is carried out, then the prepared positive electrode material is put into the battery shell, the electrolyte and the negative electrode material are added, and finally the battery shell is covered to package the lithium ion battery. ​

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