Lithium ion positive electrode material doped with tin ions and fluorine ions and preparation method of lithium ion positive electrode material

Abstract

The invention discloses a tin ion and fluorine ion doped lithium ion positive electrode material and a preparation method thereof, the tin ion and fluorine ion doped lithium ion positive electrode material comprises a chemical formula of Li < 1.3 > Mn < 0.5-0.5 > x Nb < 0.2-0.5 > x Sn < x > O < 1.8 > F < 0.2 >, and x is 0.02, 0.05, 0.1, 0.15 and 0.2. The invention relates to the technical field of lithium ion batteries, and has the beneficial effects that the lithium ion positive electrode material has high specific capacity and has a unique three-dimensional ion transmission channel, so that lithium ions have better transmission efficiency; and the positive electrode material has excellent stability, and promotes the reversible oxidation-reduction reaction of oxygen. The positive electrode material also has the characteristics of good economic benefits and flexible components, and expensive metal materials are not needed.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, and in particular to a lithium-ion cathode material doped with tin ions and fluorine ions and its preparation method. Background Technology

[0002] In recent years, numerous studies have shown that lithium-rich Mn-based disordered rock salt cathode materials (DRX) are highly attractive cathode materials, such as Li... 1.2 Mn 0.7 Nb 0.1 O 1.8 F 0.2 Li 1.15 Ni 0.45 Ti 0.3 Mo 0.1 O 1.85 F 0.15 Li 1.3 Ta 0.3 Mn 0.4 O2, each of them can provide >1000Wh / kg -1 Energy density and >300mAh g -1 The specific capacity. Compared with traditional layered oxides, lithium-excess disordered rock salt oxides have a more stable structure and higher extractable Li. + In addition to the content of oxygen, the redox reaction of oxygen provides additional electron capacity to the material. However, since an inert high-valence transition metal (TM) is required to compensate for the excess Li, this will reduce the total redox content of TM. The redox reaction of oxygen may lead to O loss and cause problems such as structural instability, rapid capacity decay, and poor cycling stability.

[0003] To address the above problems, doping is commonly used for modification. However, single-element doping cannot effectively solve these issues. For example, doping with Li... 1.3 Mn 0.4 Nb 0.3 While single anion substitution of O2 may alleviate voltage decay and suppress lattice oxygen release, it may reduce lithium-ion diffusion kinetics; while single cation doping may improve structural stability, it may introduce lattice defects that affect the continuity of lithium-ion diffusion channels.

[0004] For lithium-rich manganese-based disordered rock salt cathode materials Li 1.3 Mn 0.4 Nb 0.3 O2 was modified by co-doping with anions and cations, and F was added respectively. - and Sn 4+ To improve the specific capacity and capacity retention of the original substrate, and by regulating Sn 4+ To investigate the proportion of Sn doping 4+The optimal content. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned problems by designing a lithium-ion cathode material doped with tin ions and fluorine ions and its preparation method.

[0006] The technical solution of the present invention to achieve the above objectives is a lithium-ion cathode material doped with tin ions and fluorine ions and its preparation method, comprising a lithium-ion cathode material with the chemical formula Li 1.3 Mn 0.5-0.5x Nb 0.2-0.5x Sn x O 1.8 F 0.2 , where x takes values ​​of 0.02, 0.05, 0.1, 0.15, and 0.2.

[0007] A method for preparing a lithium-ion cathode material doped with tin ions and fluorine ions includes the following steps:

[0008] Step 1: Weigh the precursors SnO2, LiF, Li2CO3, Nb2O5, and Mn2O3 in stoichiometric ratio, and perform preliminary grinding in an agate mortar to obtain mixture a;

[0009] Step 2: Mixture a with ethanol and wet ball mill using a planetary ball mill for 6 hours to obtain mixture b;

[0010] Step 3: Place the ball-milled mixture b into a vacuum drying oven and dry overnight. Then, sinter it in a tube furnace under an argon atmosphere at 950°C for 12 hours at a heating rate of 5°C / min. Allow it to cool naturally to room temperature. Then, thoroughly wash away excess LiF from the powder with deionized water and dry it in a vacuum drying oven for 12 hours to obtain the lithium-ion cathode material.

[0011] Preferably, in step one: LiF is in excess by 50%, and Li2CO3 is in excess by 10%.

[0012] Preferably, in step one: the ground powder is placed in a zirconia ball mill jar, and 10 large zirconia balls and 10 small zirconia balls are placed in the jar at a ball-to-material ratio of 50:1.

[0013] Preferably, in step two: the mixture a is ball-milled with ethanol as solvent at 400 rpm for 30 minutes, then stopped for 5 minutes, and the cycle is repeated for a total duration of 6 hours.

[0014] This invention discloses a lithium-ion cathode material doped with tin and fluorine ions, and its preparation method. The lithium-ion cathode material exhibits high specific capacity and a unique three-dimensional ion transport channel, resulting in better lithium-ion transport efficiency. Furthermore, the cathode material demonstrates excellent stability, promoting reversible oxidation-reduction reactions of oxygen. This cathode material also offers good economic benefits and flexible composition, eliminating the need for expensive metal materials. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the preparation process of a lithium-ion cathode material doped with tin and fluorine ions, as described in this invention.

[0016] Figure 2 This is an XRD pattern of a lithium-ion cathode material doped with tin ions and fluorine ions and its preparation method as described in this invention.

[0017] Figure 3 These are SEM and EDS images of Example 3 of the lithium-ion cathode material doped with tin ions and fluorine ions and its preparation method described in this invention.

[0018] Figure 4 This is a TEM image of Example 3 of the lithium-ion cathode material doped with tin and fluorine ions and its preparation method described in this invention. Figure 4 In (a), the FFT is the result of the Fast Fourier Transform. Figure 4 In (b), IFFT is the corresponding inverse fast Fourier transform;

[0019] Figure 5 This invention relates to a lithium-ion cathode material doped with tin and fluorine ions and its preparation method. 1.3 Mn 0.5 Nb 0.2 O 1.8 F 0.2 (LMNOF) and Li 1.3 Mn 0.45 Nb 0.15 Sn 0.1 O 1.8 F 0.2 (LMNOFS0.1) XPS comparison chart, where LMNOF represents Comparative Example 2 and LMNOFS0.1 represents Example 3;

[0020] Figure 6 These are the first charge-discharge curves of Comparative Examples 1, 2, and 3 of the lithium-ion cathode material and its preparation method doped with tin and fluorine ions as described in this invention.

[0021] Figure 7This is a long-cycle comparison diagram of Comparative Example 1, Comparative Example 2 and Example 3 of the lithium-ion cathode material doped with tin ions and fluorine ions and its preparation method described in this invention.

[0022] Figure 8 This is a comparison chart of the rate performance of Comparative Examples 1, 2, and 3 of the lithium-ion cathode material doped with tin and fluorine ions and its preparation method described in this invention. The rate performance of the material is studied by the specific capacity at different current densities (10 mA / g, 20 mA / g, 40 mA / g, 100 mA / g, 200 mA / g, 10 mA / g).

[0023] Figure 9 This is a long-cycle comparison diagram of different Sn doping amounts in the lithium-ion cathode material and its preparation method described in this invention. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings, such as... Figure 1-9 As shown, a lithium-ion cathode material doped with tin ions and fluorine ions and its preparation method are disclosed.

[0025] Example 1

[0026] This embodiment provides a lithium-ion cathode material doped with tin and fluorine ions, with the chemical formula Li. 1.3 Mn 0.49 Nb 0.19 Sn 0.02 O 1.8 F 0.2 The preparation method is as follows:

[0027] Step 1: Weigh out SnO2, LiF, Li2CO3, Nb2O5, and Mn2O3 in stoichiometric proportions (LiF in 50% excess and Li2CO3 in 10% excess). Use an agate mortar to preliminarily mix the weighed powders. Place the ground powder into a zirconia ball mill jar to obtain mixture a. Place 10 large zirconia balls and 10 small zirconia balls in the ball mill jar at a ball-to-material ratio of 50:1.

[0028] Step 2: Using ethanol as a solvent, ball mill the powder at 400 rpm for 30 minutes, then stop for 5 minutes, repeat the cycle for a total of 6 hours to obtain mixture b.

[0029] Step 3: After the ball-milled mixture b is dried in a vacuum drying oven for 12 hours, it is placed in a corundum boat and sintered in a tube furnace with an argon atmosphere at 950°C for 12 hours at a heating rate of 5°C / min. After natural cooling to room temperature, the LiF in the powder is thoroughly washed away with deionized water, and then vacuum dried for 12 hours to obtain the lithium-ion cathode material.

[0030] Example 2

[0031] This embodiment provides a lithium-ion cathode material doped with tin and fluorine ions, with the chemical formula Li. 1.3 Mn 0.475 Nb 0.175 Sn 0.05 O 1.8 F 0.2 The preparation method is as follows:

[0032] Step 1: Weigh out SnO2, LiF, Li2CO3, Nb2O5, and Mn2O3 in stoichiometric proportions (LiF in 50% excess and Li2CO3 in 10% excess). Use an agate mortar to preliminarily mix the weighed powders. Place the ground powder into a zirconia ball mill jar to obtain mixture a. Place 10 large zirconia balls and 10 small zirconia balls in the ball mill jar at a ball-to-material ratio of 50:1.

[0033] Step 2: Using ethanol as a solvent, ball mill the powder at 400 rpm for 30 minutes, then stop for 5 minutes, repeat the cycle for a total of 6 hours to obtain mixture b.

[0034] Step 3: After the ball-milled mixture b is dried in a vacuum drying oven for 12 hours, it is placed in a corundum boat and sintered in a tube furnace with an argon atmosphere at 950°C for 12 hours at a heating rate of 5°C / min. After natural cooling to room temperature, the LiF in the powder is thoroughly washed away with deionized water, and then vacuum dried for 12 hours to obtain the lithium-ion cathode material.

[0035] Example 3

[0036] This embodiment provides a lithium-ion cathode material doped with tin and fluorine ions, with the chemical formula Li. 1.3 Mn 0.45 Nb 0.15 Sn 0.1 O 1.8 F 0.2 The preparation method is as follows:

[0037] Step 1: Weigh out SnO2, LiF, Li2CO3, Nb2O5, and Mn2O3 in stoichiometric proportions (LiF in 50% excess and Li2CO3 in 10% excess). Use an agate mortar to preliminarily mix the weighed powders. Place the ground powder into a zirconia ball mill jar to obtain mixture a. Place 10 large zirconia balls and 10 small zirconia balls in the ball mill jar at a ball-to-material ratio of 50:1.

[0038] Step 2: Using ethanol as a solvent, ball mill the powder at 400 rpm for 30 minutes, then stop for 5 minutes, and repeat the cycle to obtain mixture b. The total time is 6 hours.

[0039] Step 3: After the ball-milled mixture b is dried in a vacuum drying oven for 12 hours, it is placed in a corundum boat and heat-treated at 950°C for 12 hours in a tube furnace with an argon atmosphere. Then, the LiF in the powder is thoroughly washed away with deionized water, and the powder is vacuum dried for 12 hours to obtain the lithium-ion cathode material.

[0040] Example 4

[0041] This embodiment provides a lithium-ion cathode material doped with tin and fluorine ions, with the chemical formula Li. 1.3 Mn 0.425 Nb 0.125 Sn 0.15 O 1.8 F 0.2 The preparation method is as follows:

[0042] Step 1: Weigh out SnO2, LiF, Li2CO3, Nb2O5, and Mn2O3 in stoichiometric proportions (LiF in 50% excess and Li2CO3 in 10% excess). Use an agate mortar to preliminarily mix the weighed powders. Place the ground powder into a zirconia ball mill jar to obtain mixture a. Place 10 large zirconia balls and 10 small zirconia balls in the ball mill jar at a ball-to-material ratio of 50:1.

[0043] Step 2: Using ethanol as a solvent, ball mill the powder at 400 rpm for 30 minutes, then stop for 5 minutes, and repeat the cycle to obtain mixture b. The total time is 6 hours.

[0044] Step 3: After the ball-milled mixture b is dried in a vacuum drying oven for 12 hours, it is placed in a corundum boat and sintered in a tube furnace with an argon atmosphere at 950°C for 12 hours at a heating rate of 5°C / min. After natural cooling to room temperature, the LiF in the powder is thoroughly washed away with deionized water, and then vacuum dried for 12 hours to obtain the lithium-ion cathode material.

[0045] Example 5

[0046] This embodiment provides a lithium-ion cathode material doped with tin and fluorine ions, with the chemical formula Li. 1.3 Mn 0.4 Nb 0.1 Sn 0.2 O 1.8 F 0.2 The preparation method is as follows:

[0047] Step 1: Weigh out SnO2, LiF, Li2CO3, Nb2O5, and Mn2O3 in stoichiometric proportions (LiF in 50% excess and Li2CO3 in 10% excess). Use an agate mortar to preliminarily mix the weighed powders. Place the ground powder into a zirconia ball mill jar to obtain mixture a. Place 10 large zirconia balls and 10 small zirconia balls in the ball mill jar at a ball-to-material ratio of 50:1.

[0048] Step 2: Using ethanol as a solvent, ball mill the powder at 400 rpm for 30 minutes, then stop for 5 minutes, and repeat the cycle to obtain mixture b. The total time is 6 hours.

[0049] Step 3: After the ball-milled mixture b is dried in a vacuum drying oven for 12 hours, it is placed in a corundum boat and sintered in a tube furnace with an argon atmosphere at 950°C for 12 hours at a heating rate of 5°C / min. After natural cooling to room temperature, the LiF in the powder is thoroughly washed away with deionized water, and then vacuum dried for 12 hours to obtain the lithium-ion cathode material.

[0050] Comparative Example 1

[0051] This comparative example provides a lithium-ion cathode material with the chemical formula Li. 1.3 Mn 0.4 Nb 0.3 O2, prepared as follows:

[0052] Step 1: Weigh out Li2CO3, Nb2O5, and Mn2O3 in stoichiometric proportions (Li2CO3 in excess by 10%). Use an agate mortar to preliminarily mix the weighed powders. Place the ground powder into a zirconia ball mill jar to obtain mixture a. Place 10 large zirconia balls and 10 small zirconia balls in the ball mill jar at a ball-to-material ratio of 50:1.

[0053] Step 2: Using ethanol as a solvent, ball mill the powder at 400 rpm for 30 minutes, then stop for 5 minutes, and repeat the cycle to obtain mixture b. The total time is 6 hours.

[0054] Step 3: After the ball-milled mixture b is dried in a vacuum drying oven for 12 hours, it is placed in a corundum boat and sintered in a tube furnace with an argon atmosphere at 950°C for 12 hours at a heating rate of 5°C / min. The mixture is then naturally cooled to room temperature to obtain the lithium-ion cathode material.

[0055] Comparative Example 2

[0056] This comparative example provides a fluorine-doped lithium-ion cathode material with the chemical formula Li. 1.3 Mn 0.5 Nb 0.2 O 1.8 F0.2 The preparation method is as follows:

[0057] Step 1: Weigh out the stoichiometric amounts of LiF, Li2CO3, Nb2O5, and Mn2O3 (LiF in 50% excess and Li2CO3 in 10% excess). Use an agate mortar to preliminarily mix the weighed powders. Place the ground powder into a zirconia ball mill jar to obtain mixture a. Place 10 large zirconia balls and 10 small zirconia balls in the ball mill jar at a ball-to-material ratio of 50:1.

[0058] Step 2: Using ethanol as a solvent, ball mill the powder at 400 rpm for 30 minutes, then stop for 5 minutes, and repeat the cycle to obtain mixture b. The total time is 6 hours.

[0059] Step 3: After the ball-milled mixture b is dried in a vacuum drying oven for 12 hours, it is placed in a corundum boat and sintered in a tube furnace with an argon atmosphere at 950°C for 12 hours at a heating rate of 5°C / min. After natural cooling to room temperature, the LiF in the powder is thoroughly washed away with deionized water, and then vacuum dried for 12 hours to obtain the lithium-ion cathode material.

[0060] The specific flow charts of the lithium-ion cathode materials in Examples 1-5 and Comparative Examples 1-2 are as follows: Figure 1 As shown.

[0061] like Figure 2 As shown, Figure 2 (a) compares the XRD patterns of Comparative Examples 1-2 and Example 3. The pattern shows that the incorporation of Sn and F elements did not significantly change the phase structure of the disordered rock salt, and there were no obvious impurity peaks, indicating successful synthesis. Figure 2 (b) The XRD patterns of Examples 1-5 were compared, showing that the incorporation of Sn did not disrupt the disordered rock salt phase structure and there were no obvious impurity peaks.

[0062] like Figure 3 As shown, the morphology of Example 3 was characterized. It can be seen that Example 3 is composed of irregular particles. The EDS diagram shows that the elements in Example 3 are evenly distributed and the particles are intact. Figure 4 This is a transmission electron microscope image of Example 3. Figure 4 (a) and Figure 4 (b) The results of Fast Fourier Transform and Inverse Fast Fourier Transform of Example 3 are respectively. The lattice spacing of Example 3 is calculated to be approximately 0.2262 nm by Fast Fourier Transform and Inverse Fast Fourier Transform.

[0063] Figure 5Images (a)-(f) compare the XPS spectra of Example 3 and Comparative Example 2. The characteristic peaks of Mn, Nb, and O show no significant changes in position or intensity after doping with tin and fluorine, indicating that the incorporation of tin and fluorine did not alter their valence state or bonding configuration. Furthermore, two distinct Sn characteristic peaks appeared in the Sn-doped sample, further confirming that Sn has been incorporated into the structure of Example 3.

[0064] The lithium-ion battery cathode materials prepared in Comparative Examples 1-2 and Examples 1-5 were used to assemble button cells, and their electrochemical performance was tested. The specific testing method included the following steps:

[0065] (1) Preparation of positive electrode material: The active material, SuperP and PVDF solution were weighed in a ratio of 8:1:1 and then stirred thoroughly for 12 hours with a magnetic stirrer to form a uniform slurry. The slurry was coated on aluminum foil and dried in a vacuum drying oven at 120°C for 6 hours. Subsequently, the dried aluminum foil was cut into circular blanks as positive electrodes.

[0066] (2) The electrolyte is a solution of 1M LiPF6 in ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1.

[0067] (3) The negative electrode is a lithium sheet.

[0068] (4) All electrochemical tests were performed on CR2025 coin cells. The cells were assembled in an argon-filled glove box (water and oxygen content <0.1ppm). The cells were tested at room temperature on a Blue Battery testing system within a voltage range of 1.5–4.8V. Intermittent galvanostatic titration (GITT) tests were performed on the same battery testing system. Electrochemical impedance spectroscopy (EIS) was performed on an electrochemical workstation with an AC amplitude of 5mV and a frequency range of 0.01Hz to 100kHz.

[0069] Test results are available Figure 6-9 As shown.

[0070] Depend on Figure 6 It can be seen that Example 3 has the highest first-cycle specific capacity compared to Comparative Examples 1 and 2, followed by Comparative Example 2, and the lowest compared to Comparative Example 1, demonstrating the superior performance of doping with tin and fluorine ions. Figure 7 As shown, Comparative Examples 1 and 2 exhibited faster capacity decay after 100 cycles, and their specific capacity was also slightly lower than that of Example 3. The rate performance of Comparative Examples 1, 2, and 3 was investigated by measuring their specific capacity at different current densities. Figure 8It can be seen that Example 3 can still maintain a high specific capacity at high rates, and its specific capacity at different current densities is significantly better than that of Comparative Example 1 and Comparative Example 2, proving that it has better structural stability and lithium-ion transport rate. Figure 9 Cycling curves after 50 cycles are shown for different Sn doping amounts, with Example 3 showing a significant advantage over the others, exhibiting higher specific capacity and capacity retention.

[0071] According to the test data, Example 3 has excellent electrochemical performance, better structural stability and lithium-ion transport rate, which is significantly better than Comparative Example 1 and Comparative Example 2.

[0072] The above technical solutions only embody the preferred technical solutions of the present invention. Any modifications that may be made by those skilled in the art to certain parts thereof embody the principles of the present invention and fall within the protection scope of the present invention.

Claims

1. A lithium-ion cathode material doped with tin ions and fluorine ions, characterized in that, Including the chemical formula Li 1.3 Mn 0.5-0.5x Nb 0.2-0.5x Sn x O 1.8 F 0.2 , where x takes values ​​of 0.02, 0.05, 0.1, 0.15, and 0.

2.

2. A method for preparing a lithium-ion cathode material doped with tin ions and fluorine ions, characterized in that, Includes the following steps: Step 1: Weigh the precursors SnO2, LiF, Li2CO3, Nb2O5, and Mn2O3 in stoichiometric ratio, and perform preliminary grinding in an agate mortar to obtain mixture a; Step 2: Mixture a with ethanol and wet ball mill using a planetary ball mill for 6 hours to obtain mixture b; Step 3: Place the ball-milled mixture b into a vacuum drying oven and dry overnight. Then, sinter it in a tube furnace under an argon atmosphere at 950°C for 12 hours at a heating rate of 5°C / min. Allow it to cool naturally to room temperature. Then, thoroughly wash away excess LiF from the powder with deionized water and dry it in a vacuum drying oven for 12 hours to obtain the lithium-ion cathode material.

3. The method for preparing a lithium-ion cathode material doped with tin ions and fluorine ions according to claim 2, characterized in that, In step one: LiF is in excess by 50%, and Li2CO3 is in excess by 10%.

4. The method for preparing a lithium-ion cathode material doped with tin ions and fluorine ions according to claim 2, characterized in that, In step one: the ground powder is placed in a zirconia ball mill jar, and 10 large zirconia balls and 10 small zirconia balls are placed in the jar at a ball-to-material ratio of 50:

1.

5. The method for preparing a lithium-ion cathode material doped with tin ions and fluorine ions according to claim 2, characterized in that, In step two: using ethanol as a solvent, the mixture a is ball-milled at 400 rpm for 30 minutes, then stopped for 5 minutes, and the cycle is repeated for a total duration of 6 hours.

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