Ternary positive electrode conductive agent of lithium ion battery as well as preparation method and application of ternary positive electrode conductive agent

Abstract

The invention discloses a ternary positive electrode conductive agent of a lithium ion battery, and a preparation method and application thereof, and relates to the technical field of lithium ion batteries. The composite material is prepared from the following raw materials in percentage by mass: 95 percent to 97 percent of LiNiCoMnO2, 1.8 percent to 3.6 percent of SP and 1.2 percent to 1.4 percent of PVDF (Polyvinylidene Fluoride). The preparation method comprises the following steps: mixing and stirring NMP and PVDF to prepare a glue solution; liNiCoMnO2 and SP are added, and the mixture is stirred and mixed into ternary positive electrode conductive agent slurry with the solid content being 65%-70%. Coating an aluminum foil with the slurry, and drying to obtain a positive plate; the preparation method comprises the following steps: mixing graphite, conductive carbon black, CMC and SBR, adding deionized water, stirring and mixing to form slurry with the solid content of 40-50%, coating a copper foil with the slurry, and drying to obtain a negative plate; and carrying out tab welding on the obtained positive plate and negative plate, winding with a ceramic diaphragm to form a roll core, filling the roll core into a shell, injecting an electrolyte consisting of an electrolyte lithium salt and an organic solvent, and carrying out formation and capacity grading to obtain the lithium ion battery. According to the positive electrode conductive agent prepared by the invention, the production cost is reduced, and the cycle performance of the battery is not influenced while the process processing performance is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a ternary positive electrode conductive agent for lithium ion batteries and a preparation method and application thereof. Background Art

[0002] In order to improve the conductivity of lithium-ion materials, the positive electrode formulas of lithium-ion batteries with ternary material systems in the battery industry are mainly the following two: (1) LiNiCoMnO2, SP, KS-6, PVDF, wherein the usage range of each is: 94%~96%, 1%~3%, 0.5%~1.8%, 1.2%~1.4%; (2) LiNiCoMnO2, SP, CNT, PVDF, wherein the usage range of each is: 94%~96%, 1%~3%, 0.5%~1.3%, 1.2%~1.4%; Among them, LiNiCoMnO2: lithium nickel cobalt manganese oxide (ternary material), SP: conductive carbon black (conductive agent), KS-6: conductive graphite (conductive agent), CNT: carbon nanotube (conductive agent), PVDF: Polyvinylidene fluoride (adhesive).

[0003] The primary function of the conductive agent is to improve the electronic conductivity. In order to ensure that the electrode has good charge and discharge performance, a certain amount of conductive agent is usually added during the production of the electrode sheet to collect microcurrents between the active substances and between the active substances and the current collector, so as to reduce the contact resistance of the electrode and accelerate the movement rate of electrons. In addition, the conductive agent can also improve the processing of the electrode sheet, promote the infiltration of the electrolyte into the electrode sheet, and effectively increase the migration rate of lithium ions in the electrode material, reduce polarization, and thus improve the charge and discharge efficiency of the electrode and the service life of the lithium battery. However, in the existing formula, the viscosity performance of the CNT slurry changes greatly during storage, which affects the process processing. The imported production volume of KS-6 is small and cannot fully meet the industry's demand.

[0004] In order to solve the above problems, the present invention provides a novel ternary positive electrode conductive agent for lithium ion batteries and a preparation method thereof. Summary of the invention

[0005] The purpose of the present invention is to provide a ternary positive electrode conductive agent for lithium ion batteries, a preparation method and an application thereof, so as to solve the problems mentioned in the above background technology, reduce production costs, improve process processing performance, and achieve the same battery cycle performance.

[0006] To achieve the above object, the present invention provides a ternary positive electrode conductive agent for a lithium ion battery, which comprises the following raw materials by mass percentage: 95%~97% LiNiCoMnO2, 1.8%~3.7% SP and 1.2%~1.3% PVDF.

[0007] The present invention also provides a method for preparing the above-mentioned ternary positive electrode conductive agent for a lithium ion battery, comprising the following steps: (1) Add NMP and PVDF into a high-speed mixer and mix them evenly, stirring to form a glue solution; (2) Add LiNiCoMnO2 and SP into a high-speed mixer and stir them evenly to form a ternary positive electrode conductive agent slurry with a solid content of 65% to 70%.

[0008] Preferably, in step (1), the parameters of the mixer are: revolution speed of 30RPM, dispersion speed of 2000RPM, and stirring time of 120min.

[0009] Preferably, in step (2), the parameters of the mixer are: revolution speed of 33 RPM, dispersion speed of 2000 RPM, and stirring time of 240 min.

[0010] The present invention also provides application of the above-mentioned ternary positive electrode conductive agent for lithium ion batteries in the preparation of lithium ion batteries.

[0011] Preferably, the specific steps of preparing the ternary positive electrode conductive agent in a lithium ion battery are: a. Use a transfer coater to coat the ternary positive electrode conductive agent slurry on an aluminum foil with a thickness of 15 μm, and dry it to obtain a positive electrode sheet; b. Graphite, conductive carbon black, CMC and SBR are mixed according to the mass ratio, and then deionized water is added in a high-speed mixer and uniformly mixed into a slurry with a solid content of 40% to 50%. The slurry is coated on a copper foil with a thickness of 8 um using a transfer coater, and dried to obtain a negative electrode sheet; c. The obtained positive electrode sheet and negative electrode sheet are welded to the tabs, and are wound with the ceramic diaphragm to form a winding core, which is placed in a shell and injected with an electrolyte consisting of electrolyte lithium salt and organic solvent, and a lithium-ion battery is obtained after formation and capacity separation.

[0012] Preferably, in step b, the amounts of graphite, conductive carbon black, CMC and SBR are 95.7%, 1.00%, 1.30% and 2.00% respectively by mass percentage.

[0013] Preferably, the electrolyte consists of 14-16% LiPF6, 45-55% DMC, 20-30% EC, 5-15% EMC, 5-7% PS and the balance VC.

[0014] Therefore, the present invention provides a ternary positive electrode conductive agent for lithium-ion batteries, a preparation method and an application thereof, which reduces the purchase and inventory of conductive agents of various models and types, reduces battery costs, improves process processing performance, and does not affect the battery cycle performance.

[0015] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a cycle performance curve diagram of the lithium ion battery prepared in Example 1 of the present invention under 0.5C charging and 5C discharging conditions; Figure 2 This is a cycle performance curve diagram of the lithium ion battery prepared in Example 2 of the present invention under 1C charging and 10C discharging conditions; Figure 3 This is a cycle performance curve diagram of the lithium ion battery prepared in Example 3 of the present invention under 1C charging and 10C discharging conditions; Figure 4 It is a cycle performance curve diagram of the lithium ion batteries prepared in Comparative Examples 1 and 2 of the present invention under 0.5C charging and 5C discharging conditions. DETAILED DESCRIPTION

[0017] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. Any other changes, modifications, substitutions, combinations, and simplifications made without violating the spirit and principle of the present invention should all be equivalent replacement methods and are included in the protection scope of the present invention. In addition, it should be understood that after reading the content of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application, and all belong to the scope of protection of the present invention.

[0018] Reference to "embodiment" herein means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The term "embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or association with other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, the various technical features mentioned in the embodiments can be combined in any way to form a corresponding implementable technical solution.

[0019] Unless otherwise defined, the technical terms used in this document have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms in this document is only for describing specific embodiments and is not intended to limit this application.

[0020] Unless otherwise specified in the present invention, the reagents, instruments, and equipment used are those commonly used by technicians in this field.

[0021] The electrolyte used in the present invention is Hangsheng electrolyte, which is composed of 14-16% LiPF6, 45-55% DMC, 20-30% EC, 5-15% EMC, 5-7% PS and the balance VC, and is a conventional commercially available product.

[0022] Example 1 This embodiment provides a method for preparing a ternary positive electrode material system lithium ion battery, comprising the following steps: (1) By mass percentage, 96.5% LiNiCoMnO2, 2.3% SP and 1.2% PVDF; (2) Add 2142.86g of NMP and 60g of polyvinylidene fluoride into a high-speed stirrer and mix them evenly. Stir for 120min at a revolution speed of 30RPM and a dispersion speed of 2000RPM to prepare a glue solution. Then add 4825g of lithium nickel cobalt manganese oxide and 115g of conductive carbon black into the high-speed stirrer and stir for 240min at a revolution speed of 33RPM and a dispersion speed of 2000RPM to evenly mix them into a ternary positive electrode conductive agent slurry with a solid content of 65% to 70%. (3) The slurry is coated on an aluminum foil with a thickness of 15 μm using a transfer coater and dried to obtain a positive electrode sheet; (4) By mass percentage, take 95.7% graphite, 1.00% conductive carbon black, 1.30% CMC and 2.00% SBR; (5) Add graphite, conductive carbon black, CMC and SBR into a high-speed mixer, then add deionized water and mix evenly into a slurry with a solid content of 40% to 50%; (6) The slurry is coated on a copper foil with a thickness of 8 μm using a transfer coater and dried to obtain a negative electrode sheet; (7) The obtained positive electrode sheet and negative electrode sheet are welded to the tabs, wound with the ceramic diaphragm to form a winding core, placed in a shell, injected with electrolyte, and subjected to formation and capacity separation to obtain a finished lithium-ion battery.

[0023] Example 2 This embodiment provides a method for preparing a lithium-ion battery with a ternary positive electrode material system, which differs from the embodiment 1 only in that, by mass percentage, 95% LiNiCoMnO2, 3.7% SP and 1.3% PVDF are used. The rest is the same as the embodiment 1 and will not be repeated here.

[0024] Example 3 This embodiment provides a method for preparing a lithium-ion battery with a ternary positive electrode material system, which differs from the embodiment 1 only in that, by mass percentage, 95.5% LiNiCoMnO2, 3.2% SP and 1.3% PVDF are used. The rest is the same as the embodiment 1 and will not be repeated here.

[0025] Comparative Example 1 This comparative example provides a method for preparing a lithium-ion battery with a ternary positive electrode material system, which differs from Example 1 only in that, by mass percentage, 96.3% LiNiCoMnO2, 1.8% SP, 0.7% KS-6 and 1.2% PVDF are used. The rest is the same as Example 1 and will not be repeated here.

[0026] Comparative Example 2 This comparative example provides a method for preparing a lithium-ion battery with a ternary positive electrode material system, which differs from Example 1 only in that, by mass percentage, 97.1% LiNiCoMnO2: 1% SP: 0.7% CNT: 1.2% PVDF is used. The rest is the same as Example 1 and will not be repeated here.

[0027] The lithium ion batteries prepared in the above-mentioned Examples 1-3 and Comparative Examples 1-2 were subjected to a discharge cycle performance test. The test results are shown in FIG. Figure 1-4 shown.

[0028] Depend on Figure 1-4 By comparison, the charge and discharge cycle curves of Examples 1-3 are smoother, the charge and discharge process curves have fewer inflection points, and the cyclability of the lithium-ion battery is significantly improved, which shows that the present invention improves the migration rate of lithium ions in the electrode material and reduces polarization, thereby improving the charge and discharge efficiency of the electrode and the service life of the entire battery. By adjusting the addition ratio of the conductive agent, more electron pathways can be constructed, reducing the resistance to lithium ion migration, thereby improving the ionic conductivity of the battery.

[0029] Depend on Figure 1 and Figure 4 By comparison, it can be seen that the high-rate cycle performance of Example 1 is improved. By improving the conductive network of the electrode material, it is helpful to improve the charge and discharge capacity of the battery at high current density, reduce the internal resistance, and alleviate the polarization phenomenon, thereby improving the cycle stability and life of the battery. Adjustment of the proportion of the conductive agent can improve the conductivity of the lithium-ion battery, reduce the internal resistance, and improve the rate performance, so that the battery performs better when charged and discharged at high currents.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A ternary positive electrode conductive agent for a lithium ion battery, characterized in that: Calculated by mass percentage, it includes the following raw materials: 95%~97%LiNiCoMnO2, 1.8%~3.7%SP and 1.2%~1.3%PVDF.

2. The method for preparing a ternary positive electrode conductive agent for a lithium ion battery according to claim 1, characterized in that: The following steps are involved: (1) Add NMP and PVDF into a high-speed mixer and mix them evenly, stirring to form a glue solution; (2) Add LiNiCoMnO2 and SP into a high-speed mixer and stir them evenly to form a ternary positive electrode conductive agent slurry with a solid content of 65% to 70%.

3. The method for preparing a ternary positive electrode conductive agent for a lithium ion battery according to claim 2, characterized in that: In step (1), the parameters of the mixer are: revolution speed is 30RPM, dispersion speed is 2000RPM, and stirring time is 120min.

4. The method for preparing a ternary positive electrode conductive agent for a lithium ion battery according to claim 2, characterized in that: In step (2), the parameters of the mixer are: revolution speed is 33RPM, dispersion speed is 2000RPM, and stirring time is 240min.

5. The use of a ternary positive electrode conductive agent for a lithium ion battery as claimed in claim 1, characterized in that: The ternary positive electrode conductive agent is used in the preparation of lithium ion batteries.

6. The use of a ternary positive electrode conductive agent for a lithium ion battery according to claim 5, characterized in that: The specific steps of preparing the ternary positive electrode conductive agent in a lithium ion battery are: a. Use a transfer coater to coat the ternary positive electrode conductive agent slurry on an aluminum foil with a thickness of 15 μm, and dry it to obtain a positive electrode sheet; b. Add graphite, conductive carbon black, CMC and SBR into a high-speed mixer according to the mass ratio and mix them. Then add deionized water and mix them evenly into a slurry with a solid content of 40% to 50%. Use a transfer coater to coat the slurry on a copper foil with a thickness of 8 um, and dry it to obtain a negative electrode sheet. c. The obtained positive electrode sheet and negative electrode sheet are welded to the tabs, and are wound with the ceramic diaphragm to form a winding core, which is placed in a shell and injected with an electrolyte consisting of electrolyte lithium salt and organic solvent, and a lithium-ion battery is obtained after formation and capacity separation.

7. The use of a ternary positive electrode conductive agent for a lithium ion battery according to claim 6, characterized in that: In step b, the amounts of graphite, conductive carbon black, CMC and SBR are 95.7%, 1.00%, 1.30% and 2.00% respectively by mass percentage.

8. The use of a ternary positive electrode conductive agent for a lithium ion battery according to claim 6, characterized in that: In step c, the electrolyte consists of 14-16% LiPF6, 45-55% DMC, 20-30% EC, 5-15% EMC, 5-7% PS and the balance VC.

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