Preparation method of lithium supplement conductive agent and lithium ion battery

Abstract

The invention provides a preparation method of a lithium supplement conductive agent and a lithium ion battery, and relates to the technical field of lithium ion batteries. The preparation method of the lithium-supplementing conductive agent comprises the following steps: step 1, heating a mixture containing a conductive carbon material and strong acid for reaction to prepare an oxidized carbon material; and 2, mixing the oxidized carbon material prepared in the step 1 with an aqueous solution containing a lithium source, and then drying to prepare the lithium-supplementing conductive agent. According to the preparation method of the lithium-supplementing conductive agent provided by the invention, a method for oxidizing the carbon material is used, so that not only is the dispersity of the conductive agent in slurry improved, but also the use environment of the lithium-supplementing conductive agent can be widened in a manner of taking adsorbed Li < + > as a lithium source; the lithium-supplementing conductive agent prepared by the preparation method provided by the invention has a lithium-supplementing effect and does not increase other byproducts at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and particularly to a preparation method of a lithium supplement conductive agent and a lithium-ion battery. Background Art

[0002] With the rise of the new energy industry, as a secondary battery, lithium-ion batteries are widely used in fields such as mobile phones, portable computers, new energy vehicles, and energy storage devices due to their advantages of high specific capacity, long cycle life, and low self-discharge. However, with the continuous development of electric vehicles and energy storage devices, higher requirements are put forward for the energy density and cycle life of lithium-ion batteries. High specific capacity lithium supplement agents can make up for the capacity loss when the SEI film is formed during the first charging of lithium batteries, and play a great role in improving the capacity and energy density of lithium batteries. At present, the main methods of lithium supplementation are positive electrode lithium supplementation and negative electrode lithium supplementation. However, negative electrode lithium supplementation is achieved by directly adding lithium powder to the negative electrode, which has high requirements for equipment and the environment, and is difficult to achieve with current technologies. Conventional positive electrode lithium supplementation is achieved by adding some lithium-rich compounds to the positive electrode material. However, the impurities generated after the decomposition of the added lithium-rich compounds will remain in the electrode sheet, seriously affecting the conductivity of the positive electrode, increasing the polarization of the battery, and having a serious impact on the capacity and cycle life of the battery core. At the same time, lithium-rich materials are relatively sensitive to moisture, so they have high requirements for the environment during use, restricting their large-scale use. As a main component in the positive and negative electrodes, conductive agents play a role in reducing impedance in the battery. Currently, there is a patent (CN202311086566.6) that attaches Li to the surface of the conductive agent to form a lithium supplement conductive agent. However, since it coats the solid lithium supplement agent on the conductive agent, it can only be applied to oil-based systems, and its preparation process is complex and the cost is high, making it difficult to commercialize. Moreover, the lithium supplement agent is a lithium-rich compound such as lithium ferrite, and the impurities generated after decomposition will remain in the electrode sheet, seriously affecting the conductivity of the positive electrode. Summary of the Invention

[0003] In view of the above analysis, the present invention aims to provide a preparation method of a lithium supplement conductive agent and a lithium-ion battery to solve at least one of the following existing problems: improving the stability of the lithium supplement conductive agent and improving the kinetic performance of the lithium-ion battery.

[0004] The object of the present invention is mainly achieved through the following technical solutions:

[0005] In a first aspect, the present invention provides a preparation method of a lithium supplement conductive agent, including the following steps:

[0006] Step 1: Heat a mixture containing a conductive carbon material and a strong acid to react to obtain an oxidized carbon material;

[0007] Step 2: Mix the oxidized carbon material obtained in Step 1 with an aqueous solution containing a lithium source, and then dry to obtain a lithium-supplemented conductive agent.

[0008] Preferably, in Step 1, the conductive carbon material includes at least one of carbon black, carbon nanotubes, and graphene.

[0009] Preferably, in Step 1, the strong acid includes at least one of concentrated sulfuric acid and concentrated nitric acid.

[0010] Preferably, in Step 2, the lithium source includes at least one of lithium carbonate and lithium hydroxide.

[0011] Preferably, in Step 1, the reaction temperature is 45°C to 60°C.

[0012] Preferably, in Step 1, the reaction time is 6h to 12h.

[0013] Preferably, in Step 1, the ratio of the mass of the conductive carbon material to the volume of the strong acid is (0.4 - 0.6) g : (45 - 55) mL.

[0014] Preferably, in Step 2, the mass ratio of the oxidized carbon material to the lithium source is 1 : (1 - 3).

[0015] In a second aspect, the present invention provides a lithium-supplemented conductive agent prepared by the above preparation method.

[0016] In a third aspect, the present invention provides a lithium-ion battery, including an electrode sheet, a current collector of the electrode sheet, and an electrode material layer provided on the surface of the current collector, wherein the electrode material layer includes the lithium-supplemented conductive agent.

[0017] Compared with the prior art, the present invention can at least achieve one of the following beneficial effects:

[0018] A) The preparation method of the lithium-supplemented conductive agent provided by the present invention uses a method of oxidizing carbon materials, which not only improves the dispersibility of the conductive agent in the slurry, but also broadens the application environment of the lithium-supplemented conductive agent by adsorbing Li + as a lithium source. In addition, the lithium-supplemented conductive agent prepared by the preparation method provided by the present invention can play a role in lithium supplementation without increasing other by-products.

[0019] B) The preparation method of the lithium-supplemented conductive agent provided by the present invention is simple to manufacture, can reduce the manufacturing cost, and can recover Li + in the waste solution. Description of the Drawings

[0020] Figure 1 It is a schematic structural diagram of the lithium-supplemented conductive agent prepared by the preparation method provided by the present invention. Detailed Embodiments

[0021] The preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings, where the drawings form a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention.

[0022] To overcome the existing technical defects, the present invention prepares a lithium supplement conductive agent. First, a new lithium supplement conductive agent is prepared. This lithium supplement conductive material can not only play the role of lithium supplement, but also will not produce other by-products that affect the performance of the battery cell. Secondly, this lithium supplement conductive material is obtained by oxidizing and adsorbing a large amount of Li + on the conductive carbon material, which can not only improve the dispersibility of the conductive agent in the slurry, but also prevent the situation similar to the reaction of solid lithium supplement material with water, so that it can be used in any system. Finally, this material is prepared by simply oxidizing the conductive carbon material and then adsorbing Li + in the waste lithium source solution. The manufacturing method is simple. While reducing the manufacturing cost, it can play the role of recovering Li + in the waste solution.

[0023] The following is a specific description of the present invention.

[0024] In a first aspect, the present invention provides a method for preparing a lithium supplement conductive agent, comprising the following steps:

[0025] Step 1: Heating a mixture containing a conductive carbon material and a strong acid to react to obtain an oxidized carbon material with carboxyl functional groups;

[0026] Step 2: Mixing the oxidized carbon material obtained in Step 1 with an aqueous solution containing a lithium source, and then drying to obtain a lithium supplement conductive agent with lithium ions.

[0027] The method for preparing the lithium supplement conductive agent provided by the present invention uses the method of oxidizing the conductive carbon material, which not only improves the dispersion stability of the conductive agent, but also can be used under conventional conditions by supplementing lithium in the way of adsorbing Li + , thus broadening the scope of use. The method for preparing the lithium supplement conductive agent provided by the present invention can have a structure as Figure 1 shown. The conductive carbon material oxidized by the strong acid has carboxyl functional groups, and due to the presence of numerous Li + on the surface of the lithium supplement conductive agent, the transport performance of Li + in the electrode sheet is enhanced, greatly reducing the internal resistance of the battery. In addition, the adsorbed Li + acts as a lithium source and will not produce by-products while playing the role of lithium supplement, having no negative impact on the lithium battery.

[0028] In a specific embodiment of the present invention, in step 1, the conductive carbon material is at least one of carbon black, carbon nanotubes, and graphene.

[0029] In a specific embodiment of the present invention, in step 1, the strong acid is at least one of concentrated sulfuric acid and concentrated nitric acid. Among them, the concentration of concentrated sulfuric acid is 95 wt.% to 99 wt.%, preferably 98 wt.%; the concentration of concentrated nitric acid is 50 wt.% to 70 wt.%, preferably 68 wt.%.

[0030] In a specific embodiment of the present invention, in step 1, the proportional relationship between the mass of the conductive carbon material and the volume of the strong acid is conductive carbon: strong acid = (0.4 - 0.6) g: (45 - 55) mL. For example, the values within the range of 0.4 - 0.6 can be 0.4, 0.45, 0.5, 0.55, 0.6, etc., and the values within the range of 45 - 55 can be 45, 47, 50, 53, 55, etc.

[0031] In a specific embodiment of the present invention, in step 1, the reaction temperature is 45°C to 60°C, such as 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60°C, etc., preferably 45°C to 55°C; the reaction time is 6 h to 12 h, such as 6, 7, 8, 9, 10, 11, 12 h, etc., preferably 9 - 11 h.

[0032] In a specific embodiment of the present invention, in step 2, the lithium source includes at least one of lithium carbonate and lithium hydroxide. In the present invention, the lithium source can come from lithium source waste liquid, and by adopting the method of adsorbing Li + in the lithium source waste liquid, it can not only recover Li + and reduce costs, but also play a role in environmental protection.

[0033] In a specific embodiment of the present invention, in step 2, the mass ratio of the oxidized carbon material to the lithium source is 1: (1 - 3), such as 1:1, 1:1.5, 1:2, 1:2.5, 1:3, etc., preferably 1: (1 - 2).

[0034] In a specific embodiment of the present invention, in step 2, the mixing time is 6 - 12 h.

[0035] In a specific embodiment of the present invention, in step 2, the drying temperature is 60 - 100°C.

[0036] In a specific embodiment of the present invention, in step 2, the concentration of the aqueous solution containing the lithium source is 20 wt.% to 40 wt.%, such as 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, 40 wt.%, etc.

[0037] Second aspect, the present invention provides a lithium supplement conductive agent prepared by the above preparation method.

[0038] Third aspect, the present invention provides a lithium-ion battery, including an electrode sheet, the electrode sheet includes a current collector and an electrode material layer disposed on the surface of the current collector, and the electrode material layer includes the lithium supplement conductive agent.

[0039] In a specific embodiment of the present invention, the preparation method of the electrode sheet includes coating a slurry on the surface of the current collector to form an electrode material layer, and the slurry further includes CMC (sodium carboxymethyl cellulose), SBR (styrene-butadiene rubber), PAA (polyacrylic acid), graphite and water. Among them, the mass ratio of graphite: lithium supplement conductive agent: CMC: PAA: SBR is (95-98): (0.5-2): (0.1-1): (0.5-2): (0.1-1), and the solid content of the slurry is 50-55 wt.%.

[0040] Next, the preferred embodiments of the present invention will be specifically described to explain the principle of the present invention, which is not used to limit the scope of the present invention.

[0041] Unless otherwise specified, all reagents used in the following examples are commercially available products.

[0042] Example 1

[0043] (1) A preparation method of a lithium supplement conductive agent for a lithium-ion battery:

[0044] Step 1: Take 0.5 g of carbon nanotubes (tube diameter 200-500 nm, aspect ratio 60-120) and disperse them in 50 mL of concentrated sulfuric acid (concentration 98 wt%), react at 50 °C for 10 h to obtain an oxidized conductive carbon material with carboxyl functional groups;

[0045] Step 2: Disperse the oxidized conductive carbon material prepared in Step 1 in an aqueous solution containing lithium hydroxide (the concentration of lithium hydroxide in the aqueous solution containing lithium hydroxide is 30 wt.%), and the mass ratio of the conductive carbon material to lithium hydroxide is 1:1. Stir well at room temperature for 12 h, filter and dry in a vacuum oven (100 °C) to obtain a lithium supplement conductive material with Li + of.

[0046] (2) Preparation of a lithium-ion battery:

[0047] The above lithium supplement conductive material, CMC, SBR, PAA, graphite, and water are prepared into a slurry by stirring, and the slurry is coated on a current collector to obtain a negative electrode sheet. Graphite: lithium supplement conductive agent: CMC: PAA: SBR = 96.5 wt.%: 1 wt.%: 0.5 wt.%: 1.5 wt.%: 0.5 wt.%, and the solid content of the slurry is 52%.

[0048] Prepare the positive electrode sheet using a conventional formulation.

[0049] Make a battery with the above positive and negative electrode sheets and test its performance. The test results are listed in Table 1.

[0050] Example 2

[0051] This example is basically the same as Example 1, except that in the preparation method of the lithium - supplementing conductive agent, in step 1, the conductive carbon material is carbon black (average particle size is 80 nm).

[0052] Example 3

[0053] This example is basically the same as Example 1, except that in the preparation method of the lithium - supplementing conductive agent, the reaction temperature in step 1 is 60 °C.

[0054] Example 4

[0055] This example is basically the same as Example 1, except that in the preparation method of the lithium - supplementing conductive agent, the mass ratio of the oxidized conductive carbon material to lithium hydroxide in step 2 is 1:2.

[0056] Example 5

[0057] This example is basically the same as Example 1, except that in the preparation method of the lithium - supplementing conductive agent, the reaction time in step 1 is 7 h.

[0058] Comparative Example 1

[0059] Preparation of lithium - ion battery:

[0060] Prepare a slurry by stirring untreated carbon nanotubes (tube diameter 200 - 500 nm, aspect ratio 60 - 120), CMC, SBR, PAA, graphite, and water, and coat the slurry on the current collector to obtain the negative electrode sheet. Graphite: carbon nanotubes: CMC: PAA: SBR = 96.5 wt.%, 1 wt.%, 0.5 wt.%, 1.5 wt.%, 0.5 wt.%, and the solid content of the slurry is 52%. Prepare the positive electrode sheet using a conventional formulation.

[0061] Make an electric core with the above positive and negative electrode sheets and test its performance. The test results are listed in Table 1.

[0062] Comparative Example 2

[0063] (1) A preparation method of a lithium - supplementing conductive agent for lithium - ion batteries:

[0064] Take 0.5 g of the conductive carbon material carbon nanotubes (tube diameter 200 - 500 nm, aspect ratio 60 - 120) and disperse it in 50 ml of concentrated sulfuric acid (concentration 98 wt%). React at 50 °C for 10 h, then filter and dry to obtain the oxidized conductive carbon material with carboxyl functional groups.

[0065] (2) Preparation of lithium-ion battery:

[0066] Prepare a slurry by stirring the above-mentioned oxidized conductive carbon material, CMC, SBR, PAA, graphite, and water, and coat the slurry on the current collector to obtain the negative electrode sheet. Graphite: oxidized conductive carbon material: CMC: PAA: SBR = 96.5 wt.%, 1 wt.%, 0.5 wt.%, 1.5 wt.%, 0.5 wt.%, and the solid content of the slurry is 52%. Prepare the positive and negative electrode sheets using a conventional formula.

[0067] Make the above positive and negative electrode sheets into a battery and test its performance. The test results are listed in Table 1.

[0068] Comparative Example 3

[0069] This comparative example is basically the same as Example 1, except that in the preparation method of the lithium supplement conductive agent, step 1 is not included. In step 2, unoxidized carbon nanotubes are dispersed in an aqueous solution with lithium hydroxide, and the subsequent steps are continued.

[0070] Table 1 Performance tests of examples and comparative examples

[0071]

[0072]

[0073] As can be seen from Table 1, the film resistances of the lithium supplement conductive agents prepared by the preparation methods of Examples 1 - 5 of the present invention are all below 3 Ω, meeting the usage requirements. And compared with Comparative Examples 1 - 3, the lithium supplement conductive agents prepared by the preparation method of the present invention can simultaneously have a lower TSI value and DCR value, and can have a higher initial efficiency, with excellent performance.

[0074] It should be noted that the above-described embodiments are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described by referring to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than limiting words. Modifications can be made to the present invention within the scope of the claims of the present invention, and the present invention can be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A preparation method of a lithium supplement conductive agent, characterized in that, It includes the following steps: Step 1: Heat a mixture containing a conductive carbon material and a strong acid to react, and obtain an oxidized carbon material; Step 2: Mix the oxidized carbon material obtained in Step 1 with an aqueous solution containing a lithium source, and then dry it to obtain a lithium-supplemented conductive agent.

2. The preparation method according to claim 1, characterized in that, In Step 1, the conductive carbon material includes at least one of carbon black, carbon nanotubes, and graphene.

3. The preparation method according to claim 1, wherein In Step 1, the strong acid includes at least one of concentrated sulfuric acid and concentrated nitric acid.

4. The preparation method according to claim 1, wherein, In Step 2, the lithium source includes at least one of lithium carbonate and lithium hydroxide.

5. The preparation method according to any one of claims 1-4, characterized in that, In Step 1, the reaction temperature is 45°C to 60°C.

6. The preparation method according to any one of claims 1-4, characterized in that, In Step 1, the reaction time is 6 h to 12 h.

7. The preparation method according to any one of claims 1-4, characterized in that, In Step 1, the proportional relationship between the mass of the conductive carbon material and the volume of the strong acid is (0.4 - 0.6) g : (45 - 55) mL.

8. The preparation method according to any one of claims 1-4, characterized in that, In Step 2, the mass ratio of the oxidized carbon material to the lithium source is 1 : (1 - 3).

9. A lithium-supplemented conductive agent prepared by the preparation method according to any one of claims 1 - 8.

10. A lithium-ion battery, characterized in that, It includes an electrode sheet, the electrode sheet includes a current collector and an electrode material layer provided on the surface of the current collector, and the electrode material layer includes the lithium-supplemented conductive agent according to claim 9.

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