Preparation method of electrode material, electrode material, electrode and lithium ion battery

A technology of electrode materials and composite materials, applied in the field of batteries, can solve the problems of low electrode conductivity, etc., and achieve the effects of high ionic conductivity, easy mass production, and enhanced ionic conductivity.

Active Publication Date: 2020-06-26
SHENZHEN HYNETECH CO LTD
5 Cites 4 Cited by

AI-Extracted Technical Summary

Problems solved by technology

[0005] In view of the above-mentioned problem of low electrode conductivity, it is necessary to provide a pr...
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Method used

[0052] Wherein, the lithium salt can mainly play the role of conducting lithium ions, that is, to improve the ionic conductivity of the electrode material. The polymer matrix is ​​used as the matrix of the organic solid electrolyte, and the addition of appropriate plasticizers and inorganic fillers can improve the mechanical properties of the organic solid electrolyte such as strength and toughness.
[0062] Wherein, the present invention is not particularly limited to the type of conductive agent, and generally can be selected from carbon materials, because carbon materials have the advantages of strong conductivity, low density, high mechanical strength, low cost, and abundant sources. The powdered carbon material can be fully dispersed among the above-mentioned composite materials to form a conductive network in the electrode material and improve the overall electron tran...
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Abstract

The invention discloses a preparation method of an electrode material, the corresponding electrode material, an electrode and a lithium ion battery. The preparation method comprises the following steps of mixing an electrode active substance with a solid electrolyte or a precursor of the solid electrolyte, and crushing to obtain a composite material; and mixing the composite material with a conductive agent. According to the preparation method, by firstly, mixing the electrode active substance with the solid electrolyte or the precursor of the solid electrolyte to enable the electrode active substance and the solid electrolyte or the precursor of the solid electrolyte to contact fully, the ionic conductivity of the electrode active substance is effectively improved, and then mixing the obtained composite material with the conductive agent to form a conductive network, the conductivity among the composite material particles is improved. The electrode material prepared by the method is clear in gradation and has higher ionic conductivity, so that an electrode and a lithium ion battery are prepared from the material, and the cycle performance of the lithium ion battery is improved.

Application Domain

Final product manufactureNon-aqueous electrolyte accumulator electrodes +2

Technology Topic

Electrically conductiveLithium electrode +8

Image

  • Preparation method of electrode material, electrode material, electrode and lithium ion battery
  • Preparation method of electrode material, electrode material, electrode and lithium ion battery

Examples

  • Experimental program(7)
  • Comparison scheme(7)
  • Effect test(1)

Example Embodiment

[0038] The invention provides a method for preparing electrode materials. It includes the following steps.
[0039] Step S1, the electrode active material and the solid electrolyte or the precursor of the solid electrolyte are mixed and then granulated to obtain a composite material, wherein the solid electrolyte includes an organic solid electrolyte or an organic-inorganic composite solid electrolyte, and the organic-inorganic composite Solid electrolytes include organic solid electrolytes and inorganic solid electrolytes.
[0040] In this step, the purpose of first mixing the electrode active material with the solid electrolyte or the precursor of the solid electrolyte is to make the electrode active material and the solid electrolyte or the precursor of the solid electrolyte thin and fully contact in advance. The electrolyte has a high ionic conductivity, so that it can fully contact the electrode active material first, which can effectively improve the ion transport performance of the electrode active material during the charge and discharge process, thereby improving the performance of the electrode.
[0041] As mentioned above, in the traditional wet coating method for preparing electrodes, the active material, organic-inorganic solid electrolyte, binder, conductive agent, and solvent are directly mixed uniformly, and then coated on the current collector to obtain The ionic conductivity of the electrode is often low.
[0042] After a lot of research, the inventor found that mixing the organic-inorganic solid electrolyte directly with the active material does not guarantee the uniformity of the solid electrolyte dispersion in the electrode material. The solid electrolyte and the active material are in insufficient contact with a large amount of The interface causes the problem of low ionic conductivity and excessive internal resistance of the electrode itself; and the actual state of the composition and spatial distribution of the electrolyte in the electrode is too complicated. For example, the electrolyte will be adsorbed by other adhesives and conductive agents. The above method is difficult to accurately control it, and in fact it also leads to the difficulty of increasing the conductivity of the electrode itself. At the same time, if more electrolyte materials are directly added in order to increase the ionic conductivity of the electrode, it will not only get half the result with half the effort, but will also bring about problems such as increased costs, decreased proportion of active materials, and decreased battery energy density.
[0043] After clearly understanding the causes of the above-mentioned problems, the inventor improved the traditional wet coating method and proposed the method for preparing the electrode material of the present invention.
[0044] As a specific example, the method of mixing the two can be dry mixing or wet mixing.
[0045] Dry mixing specifically refers to the direct mixing of electrode active materials with organic solid electrolytes or organic-inorganic composite solid electrolytes. The mixing method can specifically be ball milling, kneading, stirring, or other materials that can refine the above two components. And full contact mixing method. After mixing, it is crushed and granulated to form mixed granulated particles. The mass ratio of the mixed electrode active material to the organic solid electrolyte or the organic-inorganic composite solid electrolyte may be (100:1) to (100:100).
[0046] Wet mixing specifically refers to mixing the electrode active material with an organic solid electrolyte or an organic-inorganic composite solid electrolyte under the condition of adding a solvent. The mixing method can specifically be ball milling, kneading, stirring, or other The above two-component materials are refined and fully contacted by mixing methods. After the mixing is completed, the solvent is removed, and then pulverized and granulated to form mixed granulated particles. Among them, the solvent used can be selected from tetrahydrofuran, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, acetonitrile, isopropyl ether, acetone, butanone, isopropanol, butane At least one of alcohol, hexane, cyclohexane, NN dimethylacetamide, N-methyl-2-pyrrolidone, benzene, toluene, dimethyl sulfoxide, carbon tetrachloride, alkene trichloride, pyrrole Kind. The mass ratio of the mixed electrode active material and the organic solid electrolyte or organic-inorganic composite solid electrolyte may be (100:10) to (100:100).
[0047] In step S1, the ratio can also be appropriately adjusted according to different electrode active materials or solid electrolytes. Optionally, the weight ratio of the electrode active material to the solid electrolyte is (100:5) to (100:30). For example, the weight ratio of the electrode active material to the solid electrolyte is (100:5), (100:10), (100:15), (100:20), (100:25) or (100:30).
[0048] If the solid electrolyte is an organic-inorganic composite solid electrolyte, the mass ratio of the organic solid electrolyte to the inorganic solid electrolyte can be (10:1) to (1:3), which can be selected according to the specific properties of different solid electrolytes.
[0049] The organic solid electrolyte may include a lithium salt, a polymer matrix, and a plasticizer.
[0050] Wherein, the mass ratio of the lithium salt to the polymer is (1:20) to (5:1), and the mass ratio of the plasticizer to the polymer is (5:100) to (60: 100).
[0051] The organic solid electrolyte may also include an inorganic filler, and calculated based on the total mass of the lithium salt, polymer, plasticizer, and inorganic filler, the mass ratio of the inorganic filler is 0%-30%.
[0052] Among them, the lithium salt can mainly play the role of conducting lithium ions, that is, improving the ionic conductivity of the electrode material. As the matrix of the organic solid electrolyte, the polymer matrix is ​​added with appropriate plasticizers and inorganic fillers to improve the mechanical properties such as the strength and toughness of the organic solid electrolyte.
[0053] As some specific examples, the lithium salt may be selected from lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), at least one of lithium difluorooxalate borate (LiODFB), lithium bisoxalate borate (LiBOB), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), and lithium bisfluorosulfonimide (LiFSI) .
[0054] The polymer can be selected from polyethylene oxide (PEO), polypropylene carbonate (PPC), polyvinyl carbonate (PEC), polytrimethylene carbonate (PTMC), polyε-caprolactone (PCL), At least one of cyano rubber (NBR) and polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP).
[0055] The plasticizer can be selected from at least one of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) .
[0056] The inorganic filler can be selected from aluminum oxide (Al 2 O 3 ), titanium dioxide (TiO 2 ), silicon dioxide (SiO 2 ), lithium phosphate (Li 3 PO 4 ), zirconium dioxide (ZrO 2 ), silicon nitride (Si 3 N 4 ), magnesium oxide (MgO), lithium aluminate (LiAlO 2 ), at least one of montmorillonite and kaolin.
[0057] The inorganic solid electrolyte can be selected from lithium phosphate, lithium aluminate, lithium lanthanum titanium oxide, neodymium or tantalum doped lithium lanthanum titanium oxide, lithium titanium aluminum phosphate, lithium germanium aluminum phosphate, lithium lanthanum zirconium titanium oxide, lithium lanthanum zirconate, and At least one of lithium nitride.
[0058] The electrode active material may specifically be a positive electrode active material or a negative electrode active material.
[0059] As some specific examples, the positive active material can be selected from LiCoO 2 , LiNiO 2 , LiNi x Co 1-x O 2 , LiNi 0.85 Co 0.1 Al 0.05 O 2 , LiNi 1/3 Mn 1/3 Co 1/3 O 2 , LiNi 0.8 Mn 0.1 Co 0.1 O 2 , LiNi 0.6 Mn 0.2 Co 0.2 O 2 , LiNi 0.5 Mn 0.2 Co 0.3 O 2 , LiMn 2 O 4 , LiNi 0.5 Mn 1.5 O 4 , LiFePO 4 , LiMnPO 4 , Li[Li x (MnNi) 1-x ]O 2 , Li[Li x (MnCo) 1-x ]O 2 And Li[Li x (MnFe) 1-x ]O 2 At least one of them.
[0060] The negative electrode active material may be selected from at least one of metallic lithium, lithium alloy, graphite, amorphous carbon, mesophase carbon microspheres, silicon carbon material, nano silicon, and lithium titanate.
[0061] Step S2, mixing the composite material obtained in step S1 with a conductive agent.
[0062] Among them, the type of conductive agent in the present invention is not particularly limited, and generally can be selected from carbon materials, because carbon materials have the advantages of strong conductivity, low density, high mechanical strength, low cost, and abundant sources. The powdered carbon material can be fully dispersed between the above composite materials to form a conductive network in the electrode material and improve the overall electron transport performance of the electrode.
[0063] Taking carbon materials as an example, the commonly used powdered conductive agents themselves have a large specific surface area. When solving the problem of low electrode ion conductivity, the applicant found that in the traditional wet coating process, the components of the electrode material are directly mixed, and the powdered conductive agent adsorbs a large amount of solid electrolyte, resulting in solid electrolyte and electrode active material Insufficient contact. In the present invention, the solid electrolyte and the electrode active material are mixed to make full contact, and then the conductive agent is mixed with the composite material obtained after mixing, so as to effectively improve the above problems.
[0064] On the other hand, the present invention also provides an electrode material prepared by the above preparation method.
[0065] Furthermore, the present invention also provides an electrode prepared according to the above-mentioned electrode material.
[0066] Wherein, the electrode may be a self-supporting electrode formed directly from the above electrode material. The forming method can be, but is not limited to, a rolling method. The rolling method can be carried out at room temperature (25°C) or under certain heating conditions. The heating temperature can be 30°C to 200°C, and can be selected according to the specific conditions of the electrode material, for example, it can be 30°C, 50°C, 80°C, 100°C, or 200°C.
[0067] The electrode may also be formed by coating the above-mentioned electrode material with a coating layer on the current collector. The method of formation is, for example, mixing with a solvent and preparing a slurry, then coating on the current collector to form a coating layer, and then removing the solvent.
[0068] Another advantage of the electrode prepared from the above electrode material is that it can be free of binders, which can reduce the quality of the inactive materials of the electrode, thereby increasing the energy density of the battery and reducing the cost of the battery.
[0069] The present invention also provides a lithium ion battery, including a positive electrode, a negative electrode, and an electrolyte. The electrolyte is arranged between the positive electrode and the negative electrode to isolate the positive electrode and the negative electrode. At least one of them is the aforementioned electrode.

Example Embodiment

[0072] Example 1: Lithium Cobalt Oxide Cathode
[0073] (1) The cathode active material is a lithium cobalt oxide cathode material with a median particle size of 5um; the lithium salt in the organic solid electrolyte selected is LiFSI, the polymer is PVDF-HFP, the plasticizer is EC, and the inorganic filler is Al 2 O 3 , The mass ratio of lithium salt and polymer is 5:1, the mass ratio of plasticizer to polymer is 60:100, and the mass ratio of inorganic filler is 1%.
[0074] (2) Adopting dry mixing method to mix, the above-mentioned lithium cobaltate and organic solid electrolyte are mixed by ball milling in a weight ratio of 100:5, and after mixing, they are mechanically crushed to form an active material-electrolyte composite material.
[0075] (3) The active material-electrolyte composite material and the conductive carbon black Super-P are uniformly mixed in a weight ratio of 100:10, and the electrode is formed by a hot rolling method, and the rolling temperature is 200°C.

Example Embodiment

[0076] Example 2: Graphite negative electrode
[0077] (1) The anode active material is graphite anode material with a median particle size of 8um; in the selected organic-inorganic composite solid electrolyte, the lithium salt in the organic electrolyte is LiTFSI, the polymer is PEO, the plasticizer is DMC, and no added Inorganic filler, the mass ratio of lithium salt and polymer is 1:20, and the mass ratio of plasticizer to polymer is 5:100; the inorganic electrolyte is lithium titanium aluminum phosphate. The mass ratio of organic electrolyte and inorganic electrolyte is 10:1.
[0078] (2) Adopt wet mixing method to mix, the above-mentioned graphite and organic-inorganic solid electrolyte are mixed in a kneader according to a weight ratio of 100:10 in a kneading method, and tetrahydrofuran is selected as the solvent. After mixing, the solvent is heated to volatilize, and then mechanically crushed to form an active material-electrolyte composite material.
[0079] (3) The active material-electrolyte composite material and the vapor-phase process carbon fiber VGCF are uniformly mixed in a weight ratio of 100:5, and the electrode is formed by a rolling method, and the rolling temperature is normal temperature (25°C).
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PUM

PropertyMeasurementUnit
Median particle size5.0µm
Median particle size8.0µm
Median particle size6.0µm
tensileMPa
Particle sizePa
strength10

Description & Claims & Application Information

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