A lithium-ion battery and its preparation method

Abstract

This application discloses a lithium-ion battery and its preparation method. The preparation method of the lithium-ion battery is as follows: (1) Manganese acetate tetrahydrate is dissolved in isopropanol / glycerol and stirred evenly; (2) Boron source and zirconium source are added to the solution in step (1) as dopants and stirred evenly; (3) The solution in step (2) is placed in a microwave hydrothermal instrument for heating reaction, the reaction temperature is controlled between 150-180℃, and the reaction time is 20-40min; (4) The product in step (3) is washed and dried to obtain negative electrode active material B / Zr-MnO2; (5) The negative electrode active material, binder, and conductive agent are mixed with solvent and coated onto the negative electrode current collector to prepare a negative electrode sheet; the negative electrode sheet, positive electrode sheet, and separator are assembled into a coin cell and injected with electrolyte to encapsulate to obtain a lithium-ion battery. B / Zr-MnO2 has a porous structure, and B / Zr co-doping effectively improves the cycle performance and rate performance of the lithium-ion battery.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage device technology, specifically to a lithium-ion battery and its preparation method. Background Technology

[0002] In recent years, with the intensification of the energy crisis and the aggravation of environmental pollution, people have been conducting increasingly in-depth research on new energy materials. Lithium-ion batteries, as an environmentally friendly, green, and efficient energy storage device, have been widely used in people's daily lives, such as in portable electronic devices, electric vehicles, and energy storage systems. As a core component of lithium-ion batteries, the negative electrode material directly affects the battery's cycle performance and rate performance. Therefore, researching and developing electrode materials with high specific capacity, high cycle performance, and good conductivity is of significant practical importance.

[0003] Compared with traditional graphite anode materials, transition metal oxides, such as manganese dioxide, have high theoretical capacity and abundant resources as lithium-ion battery anode materials, but they also have many shortcomings, such as large volume expansion during charging and discharging, low conductivity, and high irreversible capacity during the first charge and discharge, resulting in poor rate performance and cycle performance.

[0004] To address the aforementioned issues, various measures have been investigated to improve electrochemical performance. For example, nano-sizing reduces particle size, improving conductivity and cycle performance; composites with carbon materials or polymers enhance conductivity; and doping with other elements improves structural stability. For instance, patent CN115385381B discloses a method for coating manganese dioxide using a co-precipitation of copper salts, molybdates, and folic acid. During high-temperature calcination, a coating layer of molybdenum oxide, elemental copper, and nitrogen-doped carbon is generated, improving the conductivity of manganese oxide. CN115064683B synthesizes various manganese oxide@nanotube anode materials by adjusting the carbon coating, annealing atmosphere, and annealing temperature. These materials contain two phases of nanoscale composite nanotubes (MnO / Mn3O4, MnO2 / Mn3O4). Because these materials contain manganese ions in multiple valence states, the synergistic effect between these ions through electron transitions significantly improves the battery performance of manganese oxides. CN114314669B discloses a method for preparing δ-MnO2, a lithium-ion battery anode material using MOF as a template, wherein δ-MnO2 possesses a nano-hierarchical porous structure. Existing technologies for preparing manganese dioxide materials are relatively complex, or only address single aspects of manganese dioxide performance. Therefore, finding a simpler process to prepare manganese dioxide anode materials with good rate performance and high cycle stability is a current technical challenge. Based on this, this application is proposed. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a lithium-ion battery anode material, the preparation method of which is as follows:

[0006] (1) Dissolve manganese acetate tetrahydrate in isopropanol / glycerol, with a volume ratio of isopropanol / glycerol of 4-5:1; stir until homogeneous; (2) Add boron source and zirconium source as dopants to the solution obtained in step (1) and stir until homogeneous;

[0007] (3) Place the solution that was mixed evenly in step (2) into a microwave hydrothermal apparatus and heat it to react. The reaction temperature is controlled between 150-180℃ and the reaction time is 20-40min.

[0008] (4) After the reaction is complete, centrifuge, wash and dry to obtain the final product B / Zr-MnO2.

[0009] The boron source is boric acid, and the zirconium source is zirconium nitrate or zirconium chloride.

[0010] The molar ratio of manganese acetate tetrahydrate, boron source, and zirconium source is 1:(0.01-0.05):(0.01-0.05).

[0011] B / Zr-MnO2 is mixed evenly with conductive agent and binder in a certain mass ratio in a solvent, coated onto negative electrode current collector, dried to obtain electrode sheet, which is then assembled with lithium metal sheet and separator to form a coin cell, injected with electrolyte and encapsulated to obtain lithium-ion battery.

[0012] The diaphragm is made of polyethylene, polypropylene, or a polypropylene / polyethylene diaphragm.

[0013] The electrolyte comprises a lithium salt and a solvent. The lithium salt is selected from one or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium tetrafluorooxalate phosphate, or lithium bis(oxalate)borate. The solvent is selected from one or more of diethyl carbonate, ethyl methyl carbonate, propylene carbonate, dimethyl carbonate, and ethylene carbonate.

[0014] Compared with the prior art, this application can achieve the following technical effects:

[0015] The doping of B in this application helps stabilize the crystal structure, thereby mitigating the volume change of manganese dioxide during charge and discharge, and extending the battery cycle life. It also expands the lattice spacing, forming more lithium-ion diffusion channels, thus significantly improving the lithium-ion battery's transport rate. By doping manganese dioxide with B, impurity energy levels are introduced, increasing the number of free electrons / holes and improving the electronic conductivity of MnO2, thereby improving the battery's rate performance. Furthermore, the B / Zr-MnO2 exhibits a porous structure; this rich and well-developed pore structure facilitates better electrolyte wetting of the electrodes, ensuring sufficient contact between the electrolyte and electrode materials, and improving the ion transport rate. In addition, the porous structure effectively buffers the volume changes during ion insertion and extraction, reducing volume stress and improving the battery's cycle life. (See attached figures.)

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0017] Figure 1 This is a scanning electron microscope image of B / Zr-MnO2 prepared from the material of this invention.

[0018] Figure 2 These are XRD patterns of the lithium-ion battery anode materials of Embodiment 1 and Comparative Examples 1-3 of the present invention.

[0019] Figure 3 These are the rate performance diagrams of lithium-ion batteries in Embodiment 1 and Comparative Examples 1-3 of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the invention, not all of them. Therefore, the following detailed description of the embodiments of the invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention. Based on the embodiments of the invention, those skilled in the art can select appropriate embodiments within the scope of the text.

[0021] Example 1

[0022] (1) Dissolve 5 mmol of manganese acetate tetrahydrate in isopropanol / glycerol at a volume ratio of 5:1; stir for 20 min until homogeneous; (2) Add 0.1 mmol boric acid and 0.1 mmol zirconium nitrate as dopants to the solution obtained in step (1) and stir for 20 min to make it uniform;

[0023] (3) Place the solution that was mixed evenly in step (2) into a microwave hydrothermal apparatus and heat it to react. The reaction temperature is controlled at 150°C and the reaction time is 20 min.

[0024] (4) After the reaction was completed, the product was washed by alternating centrifugation with deionized water and alcohol, and then dried to obtain the final product B / Zr-MnO2.

[0025] (5) Using B / Zr-MnO2 as the negative electrode active material, polyvinylidene fluoride as the binder, and superconducting carbon black as the conductive agent, the mass ratio of negative electrode active material / binder / conductive agent is 8:1:1; the above materials are added dropwise with NMP and mixed evenly, coated on copper foil, dried, and sliced ​​to obtain the negative electrode of the lithium-ion battery. A 1M LiPF6 solution is dissolved in ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate (volume ratio 1:1:1) as the electrolyte, lithium foil is used as the counter electrode, and polyethylene film is used as the separator to assemble a coin cell lithium-ion battery.

[0026] Example 2

[0027] (1) Dissolve 5 mmol of manganese acetate tetrahydrate in isopropanol / glycerol at a volume ratio of 4:1; stir for 20 min until homogeneous; (2) Add 0.1 mmol boric acid and 0.2 mmol zirconium nitrate as dopants to the solution obtained in step (1) and stir for 20 min to homogenize;

[0028] (3) Place the solution that was mixed evenly in step (2) into a microwave hydrothermal apparatus and heat it to react. The reaction temperature is controlled at 150°C and the reaction time is 20 min.

[0029] (4) After the reaction was completed, the product was washed by alternating centrifugation with deionized water and alcohol, and then dried to obtain the final product B / Zr-MnO2.

[0030] (5) Using B / Zr-MnO2 as the negative electrode active material, polyvinylidene fluoride as the binder, and superconducting carbon black as the conductive agent, the mass ratio of negative electrode active material / binder / conductive agent is 8:1:1; the above materials are added dropwise with NMP and mixed evenly, coated on copper foil, dried, and sliced ​​to obtain the negative electrode of the lithium-ion battery. A 1M LiPF6 solution is dissolved in ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate (volume ratio 1:1:1) as the electrolyte, lithium foil is used as the counter electrode, and polyethylene film is used as the separator to assemble a coin cell lithium-ion battery.

[0031] Comparative Example 1

[0032] (1) Dissolve 5 mmol of manganese acetate tetrahydrate in isopropanol / glycerol at a volume ratio of 5:1; stir for 20 min until homogeneous; (2) Add 0.1 mmol of boric acid as a dopant to the solution obtained in step (1) and stir for 20 min to make it uniform;

[0033] (3) Place the solution that was mixed evenly in step (2) into a microwave hydrothermal apparatus and heat it to react. The reaction temperature is controlled at 150°C and the reaction time is 20 min.

[0034] (4) After the reaction was completed, the product B-MnO2 was obtained by alternating centrifugation and washing with deionized water and alcohol, followed by drying.

[0035] (5) Using B-MnO2 as the negative electrode active material, polyvinylidene fluoride as the binder, and superconducting carbon black as the conductive agent, the mass ratio of active material / binder / conductive agent is 8:1:1; the above materials are added dropwise to NMP and mixed evenly, coated on copper foil, dried, and sliced ​​to obtain the negative electrode of lithium-ion battery. 1M LiPF6 is dissolved in ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate (volume ratio of 1:1:1) as the electrolyte, lithium sheet is used as the counter electrode, and polyethylene film is used as the separator to assemble a coin cell lithium-ion battery.

[0036] Comparative Example 2

[0037] (1) Dissolve 5 mmol of manganese acetate tetrahydrate in isopropanol / glycerol at a volume ratio of 5:1; stir for 20 min until homogeneous; (2) Add 0.1 mmol of zirconium nitrate as a dopant to the solution obtained in step (1) and stir for 20 min to homogenize;

[0038] (3) Place the solution that was mixed evenly in step (2) into a microwave hydrothermal apparatus and heat it to react. The reaction temperature is controlled at 150°C and the reaction time is 20 min.

[0039] (4) After the reaction was completed, the product was washed by alternating centrifugation with deionized water and alcohol, and then dried to obtain the final product Zr-MnO2;

[0040] (5) Zr-MnO2 was used as the negative electrode active material, polyvinylidene fluoride as the binder, and superconducting carbon black as the conductive agent. The mass ratio of active material / binder / conductive agent was 8:1:1. The above materials were added dropwise to NMP and mixed evenly. The mixture was then coated on copper foil, dried, and sliced ​​to obtain the negative electrode of the lithium-ion battery. 1M LiPF6 was dissolved in ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate (volume ratio 1:1:1) as the electrolyte. A lithium sheet was used as the counter electrode, and a polyethylene film was used as the separator. The cells were then assembled into a coin cell lithium-ion battery.

[0041] Comparative Example 3

[0042] (1) Dissolve 5 mmol of manganese acetate tetrahydrate in isopropanol / glycerol at a volume ratio of 5:1; stir for 20 min until homogeneous; (2) Place the solution that was mixed evenly in step (1) into a microwave hydrothermal apparatus and heat it to react. The reaction temperature is controlled at 150℃ and the reaction time is 20min. The product is washed and dried to obtain the final product MnO2.

[0043] (3) MnO2 is used as the negative electrode active material, polyvinylidene fluoride as the binder, and superconducting carbon black as the conductive agent. The mass ratio of active material / binder / conductive agent is 8:1:1. The above materials are added dropwise to NMP and mixed evenly. The mixture is then coated on copper foil, dried, and sliced ​​to obtain the negative electrode of the lithium-ion battery. 1M lithium hexafluorophosphate is dissolved in ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate (volume ratio of 1:1:1) as the electrolyte. A lithium sheet is used as the counter electrode, and a polyethylene film is used as the separator. The cells are then assembled into a coin cell lithium-ion battery.

[0044] from Figure 2 The XRD comparison of Example 1 and Comparative Examples 1-3 shows that the crystal form of manganese dioxide did not change significantly after doping.

[0045] The discharge capacity of Example 1 and Comparative Examples 1-3 was tested at different current densities of 0.1C, 0.2C, 0.5C, 1C, 2C, and 0.1C. The results are as follows: Figure 3 As shown, the rate capability of Example 1 is significantly better than that of Comparative Examples 1-3.

[0046] The performance of lithium-ion batteries was tested after 50 cycles at 0.1C. The reversible capacity retention rate of Example 1 after 50 cycles was 93.2%, which was significantly better than that of Comparative Example 1 (87.3%), Comparative Example 2 (88.1%) and Comparative Example 3 (80.5%).

Claims

1. A method for preparing a lithium-ion battery, characterized in that, a. Preparation of the negative electrode: (1) Dissolve manganese acetate tetrahydrate in isopropanol / glycerol, with a volume ratio of isopropanol / glycerol of 4-5:1; stir until homogeneous; (2) Add boron source and zirconium source as dopants to the solution obtained in step (1) and stir until homogeneous; (3) Place the solution that has been mixed evenly in step (2) into a microwave hydrothermal apparatus and heat it to react. The reaction temperature is controlled between 150-180℃ and the reaction time is 20-40min. (4) After the reaction is complete, centrifuge, wash and dry to obtain the final product B / Zr-MnO2; (5) Mix the negative electrode active material, binder and conductive agent with a solvent, coat the negative electrode current collector, and prepare the negative electrode sheet; b. Assemble the negative electrode, lithium sheet, and separator into a coin cell, inject electrolyte, and encapsulate to obtain a lithium-ion battery.

2. In the method for preparing a lithium-ion battery according to claim 1, the boron source is boric acid, and the zirconium source is zirconium nitrate or zirconium chloride.

3. In the method for preparing a lithium-ion battery according to claim 1, the molar ratio of manganese acetate tetrahydrate, boron source, and zirconium source is 1:(0.01-0.05):(0.01-0.05).

4. The method for preparing a lithium-ion battery according to claim 1, wherein the separator is one of polyethylene, polypropylene, or polypropylene / polyethylene separator.

5. The method for preparing a lithium-ion battery according to claim 1, wherein the electrolyte comprises a lithium salt and a solvent, wherein the lithium salt is selected from one or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium tetrafluorooxalate phosphate, or lithium bis(oxalate-borate), and the solvent is selected from one or more of diethyl carbonate, ethyl methyl carbonate, propylene carbonate, dimethyl carbonate, and ethylene carbonate.

6. A lithium-ion battery, characterized in that, It is prepared by any one of claims 1-5.

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