Negative electrode material for lithium ion battery, preparation method of negative electrode material and lithium ion battery

Abstract

The invention discloses a negative electrode material for a lithium ion battery, a preparation method and the lithium ion battery, the negative electrode material has an ABX3 halide perovskite structure, A is a monovalent organic cation, B is a divalent metal cation, and X is a halogen anion. The preparation method of the negative electrode material comprises the following steps: 1) adding halide perovskite precursors: BX2 and AX into a solvent according to a stoichiometric ratio, and heating and uniformly stirring to obtain a halide perovskite precursor solution; and 2) depositing the halide perovskite precursor solution on a copper sheet current collector, and annealing to obtain the negative electrode material. The negative electrode material can be prepared into a thin film as a negative electrode through a simple solution method; performance tests and cycle tests show that the prepared lithium ion battery negative electrode material has relatively high capacity and excellent cycle stability. The lithium ion battery negative electrode material is simple in preparation method process, low in energy consumption, low in cost and beneficial to large-scale production and commercialized popularization.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium batteries, and in particular relates to a negative electrode material for a lithium ion battery, a preparation method thereof, and a lithium ion battery. Background Art

[0002] With the rapid development of mobile phones, laptops and other portable electronic devices, energy storage, electric vehicles and other emerging fields, lithium-ion batteries as new energy technologies are developing rapidly, and people have put forward higher requirements for their electrochemical performance, stability and safety. In terms of basic structure, lithium-ion batteries are mainly composed of four parts: positive electrode, negative electrode, electrolyte and separator, among which the negative electrode material is an important factor restricting its electrochemical performance.

[0003] The existing negative electrode materials for lithium-ion batteries can be generally divided into two categories: one is carbon-based negative electrode materials such as natural or artificial graphite, modified graphite, etc.; the other is non-carbon-based negative electrode materials such as metal oxides, halides, silicon, and metal alloys. These negative electrode materials all have their own shortcomings. For example, the theoretical energy density of commercial graphite carbon negative electrode materials is low and has basically reached the limit, which cannot meet people's requirements for high performance of next-generation lithium-ion batteries; and the graphite carbon negative electrode materials will cause significant changes in volume due to the frequent insertion and deinsertion of lithium ions during repeated heavy discharge, resulting in poor stability after thousands of long-term cycles. This problem is more significant for negative electrode materials such as silicon. The volume change of negative electrode materials during the repeated insertion and extraction of lithium ions leads to electrode rupture, which is the main reason for the poor cycle stability, low first coulomb efficiency, and poor reversible cyclability of lithium-ion batteries. On the other hand, the currently industrialized natural or artificial graphite negative electrode, carbon-coated graphite and other negative electrode materials also face the problems of high-temperature graphitization and subsequent coating processes, which makes the preparation process of negative electrodes based on such materials complicated and costly. Therefore, it is necessary to find and develop new negative electrode materials to meet higher requirements for cycle stability, capacity density and cost.

[0004] In recent years, metal halide perovskite materials have been widely used in solar cells, LEDs, photodetectors, lasers, and memristors. With the widespread development of related research, people have found that optoelectronic devices such as solar cells, LEDs, and photodetectors based on such materials exhibit IV hysteresis effects. In-depth research has found that this is because as an ionic crystal, the lattice structure of perovskite materials is relatively soft, which makes it easy for lattice ions to be activated by external factors such as light and voltage and leave the lattice site and migrate inside the crystal, resulting in mixed electronic and ionic conductivity. Summary of the invention

[0005] The first technical problem to be solved by the present invention is, in view of the current situation of the above-mentioned prior art, to provide a negative electrode material for a lithium-ion battery, so as to solve the problems that the preparation processes of the current negative electrode materials for lithium-ion batteries, such as graphitization and carbon coating, need to be carried out under high-temperature conditions, are complex and costly, and the deficiencies of poor battery cycling performance.

[0006] The second technical problem to be solved by the present invention is to provide a preparation method for the negative electrode material of the above-mentioned lithium-ion battery.

[0007] The third technical problem to be solved by the present invention is to provide a lithium-ion battery having the above-mentioned negative electrode material.

[0008] The technical solution adopted by the present invention to solve the above-mentioned first technical problem is: a negative electrode material for a lithium-ion battery, characterized in that: the negative electrode material has a halide perovskite structure of ABX3, where A is a monovalent organic cation, B is a divalent metal cation, and X is a halogen anion.

[0009] Preferably, the A is MA + or FA + ; the B is Pb 2+ or Sn 2+ ; the X is Cl - 、Br - or I - .

[0010] Preferably, the ABX3 is any one of MAPbI3, FAPbI3, MAPbBr3, FAPbBr3, MAPbCl3, and FAPbCl3.

[0011] Further preferably, the negative electrode material has a MAPbI3 thin film with a thickness in the micron range.

[0012] The technical solution adopted by the present invention to solve the above-mentioned second technical problem is: a preparation method for the negative electrode material as described above, characterized in that the steps are as follows:

[0013] 1) Add the halide perovskite precursors: BX2 and AX to the solvent according to the stoichiometric ratio, and heat and stir evenly to obtain a halide perovskite precursor solution;

[0014] 2) Deposit the halide perovskite precursor solution on a copper foil current collector and anneal to obtain a halide perovskite negative electrode material.

[0015] The solvent is preferably a mixed solvent of DMF and DMSO, and the mixing volume ratio of the two is 4:1 ± 0.01.

[0016] Preferably, in step 1), the temperature during heating and stirring is 50 ± 5 °C, and the time is 6 ± 0.5 h.

[0017] The concentration of the halide perovskite precursor solution affects its coverage on the copper sheet, and further affects the electrochemical performance of the electrical device. Preferably, the concentration of the halide perovskite precursor solution in step 1) is 1.2 ± 0.2 M.

[0018] Preferably, in step 2), the halide perovskite precursor solution is deposited on the copper sheet current collector by a wet film forming process such as drop coating, spin coating or blade coating, and the annealing temperature is 100 ± 5 °C.

[0019] The technical solution adopted by the present invention to solve the above-mentioned third technical problem is: a lithium-ion battery, characterized in that it has the negative electrode material as described above.

[0020] Compared with the prior art, the advantages of the present invention are as follows: As an ionic crystal, the lattice structure of the perovskite material is relatively soft, resulting in lattice ions being easily activated by external factors such as light and voltage and detaching from the lattice sites and migrating inside the crystal, thus resulting in its electron and ion mixed conductivity characteristics. However, precisely because of this soft lattice structure of the halide perovskite material, it has a high tolerance for some foreign ions, such as lithium ions, and even high-concentration lithium-ion doping will not change its lattice structure. Moreover, due to the special octahedral lattice structure of the perovskite material, the lattice interstitial space is relatively large, enabling lithium ions to have a relatively large diffusion coefficient and diffusion rate in its lattice. And the halide perovskite material lattice can accommodate an extremely high lithium-ion concentration, and during the process of lithium ions inserting and extracting from the halide perovskite negative electrode, the perovskite crystal structure deforms very little. This indicates that the halide perovskite as the negative electrode material of the lithium-ion battery has very little volume change during charge and discharge, and at the same time has a relatively high capacity density. In addition, the halide perovskite has excellent low-temperature solution self-assembly characteristics, and the preparation process is simple and the sintering temperature is low. These characteristics show that the metal halide perovskite material has great application potential in future low-cost, high-cycle-performance and high-energy-density lithium-ion batteries.

[0021] Therefore, the present invention expands the selection space of the lithium battery negative electrode material. Compared with the traditional lithium-ion battery negative electrode material, the halide perovskite lithium-ion battery negative electrode material of the present invention has stronger tolerance for lithium ions, and the preparation method is extremely simple, which is suitable for industrial production and commercial promotion and application. Brief Description of the Drawings

[0022] Figure 1 Scanning electron microscope photographs of MAPbI3 with different lithium-ion doping concentrations deposited on FTO transparent conductive glass Figure 1Among them, (a), (c), (e), (g), and (i) are low-magnification scanning electron microscope photos of lithium-ion doping concentrations of 0, 1, 2, 5, and 10 mol%, respectively, and (b), (d), (f), (h), and (j) are high-magnification scanning electron microscope photos of lithium-ion doping concentrations of 0, 1, 2, 5, and 10 mol%, respectively;

[0023] Figure 2 are structure test diagrams of MAPbI3 with different lithium-ion doping concentrations, Figure 2 Among them, (a) is an X-ray diffraction pattern, (b) is a partially enlarged X-ray diffraction pattern in (a), (c) is an ultraviolet-visible light absorption spectrum, and (d) is a fluorescence spectrum;

[0024] Figure 3 are scanning electron microscope photos of a copper metal current collector and MAPbI3 deposited on the copper metal current collector in Example 2 of the present invention, Figure 3 Among them, (a) is a low-magnification scanning electron microscope photo of the copper metal current collector, (b) and (c) are high-magnification scanning electron microscope photos of the copper metal current collector, (d) is a low-magnification scanning electron microscope photo of MAPbI3 deposited on the copper metal current collector, and (e) and (f) are high-magnification scanning electron microscope photos of MAPbI3 deposited on the copper metal current collector;

[0025] Figure 4 are X-ray diffraction patterns of a copper sheet as a current collector and the MAPbI3 negative electrode material prepared on the copper sheet in Example 2 of the present invention;

[0026] Figure 5 is the X-ray photoelectron spectrum of a copper sheet as a current collector, Figure 5 Among them, (a), (b), (c), (d), (e), and (f) are the fine spectra of Cu 2p, O 1s, Pb 4f, I 3d, N 1s, and C 1s, respectively;

[0027] Figure 6 is the X-ray photoelectron spectrum of the MAPbI3 negative electrode material prepared in Example 2 of the present invention, Figure 6 Among them, (a), (b), (c), (d), (e), and (f) are the fine spectra of Cu 2p, O 1s, Pb 4f, I 3d, N 1s, and C 1s, respectively;

[0028] Figure 7 is the charge-discharge energy curve diagram of a lithium-ion battery assembled with the MAPbI3 negative electrode material prepared in Example 2 of the present invention;

[0029] Figure 8 is the rate charge-discharge cycle performance curve diagram of a lithium-ion battery assembled with the MAPbI3 negative electrode material prepared in Example 2 of the present invention;

[0030] Figure 9 Cyclic stability curve of the lithium-ion battery assembled with the MAPbI3 negative electrode material prepared in Example 2 of the present invention;

[0031] Figure 10 X-ray diffraction pattern of the MAPbI3 negative electrode material / copper current collector prepared in Example 2 of the present invention after 200 cycles and X-ray diffraction pattern of the copper sheet obtained by rinsing the MAPbI3 negative electrode material / copper current collector prepared in Example 2 of the present invention with DMF after 200 cycles;

[0032] Figure 11 X-ray photoelectron spectrum of the copper sheet obtained by rinsing the MAPbI3 negative electrode material / copper current collector prepared in Example 2 of the present invention with DMF after 200 cycles, Figure 11 where (a), (b), (c), (d), (e), and (f) are the fine spectra of Cu 2p, O1s, Pb 4f, I 3d, N 1s, and C 1s respectively. Detailed implementation manners

[0033] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

[0034] Example 1:

[0035] The negative electrode material of this example has a halide perovskite structure of MAPbI3, and the preparation steps are as follows:

[0036] 1. Dissolve 369 ± 8 mg of PbI2 and 127 ± 8 mg of MAI in a mixed solvent of 800 ± 10 μL of DMF and 200 ± 10 μL of DMSO, and obtain a perovskite precursor solution with a concentration of 0.8 M through heating and stirring at 50 °C for 6 hours;

[0037] 2. After cleaning and drying the copper foil with ethanol, cut it into circular electrodes with a diameter of 14 mm using a slicing machine for standby. Take 50 μL of the above perovskite precursor solution, drop it on the surface of the copper foil, and then, after 20 seconds, drop 170 ± 18 μL of chlorobenzene at the center of the film. Then place the copper foil on a heating table and anneal it at 100 °C for 20 minutes to obtain a perovskite thin film / copper foil negative electrode sheet. Subsequently, use this as the negative electrode to prepare a half-cell.

[0038] Example 2:

[0039] The negative electrode material of this example has a halide perovskite structure of MAPbI3, and the preparation steps are as follows:

[0040] 1. Dissolve 461 ± 10 mg of PbI2 and 159 ± 10 mg of MAI in a mixed solvent of 800 ± 10 μL of DMF and 200 ± 10 μL of DMSO, and obtain a perovskite precursor solution with a concentration of 1.0 M through heating and stirring at 50 °C for 6 hours;

[0041] 2. After cleaning and drying the copper foil with ethanol, cut it into circular electrodes with a diameter of 14 mm using a slicing machine for standby. Take 50 μL of the above perovskite precursor solution and drop-coat it on the surface of the copper foil. Then, after 20 seconds, drop 170 ± 18 μL of chlorobenzene at the center of the film. Then, place the copper foil on a heating table and anneal it at 100 °C for 20 minutes to obtain a perovskite film / copper foil negative electrode sheet. Subsequently, use this as the negative electrode to prepare a half-cell.

[0042] Example 3:

[0043] The negative electrode material of this example has a halide perovskite structure of MAPbI3, and the preparation steps are as follows:

[0044] 1. Dissolve 553 ± 12 mg of PbI2 and 191 ± 12 mg of MAI in a mixed solvent of 800 ± 10 μL of DMF and 200 ± 10 μL of DMSO, and obtain a perovskite precursor solution with a concentration of 1.2 M through heating and stirring at 50 °C for 6 hours;

[0045] 2. After cleaning and drying the copper foil with ethanol, cut it into circular electrodes with a diameter of 14 mm using a slicing machine for standby. Take 50 μL of the above perovskite precursor solution and drop-coat it on the surface of the copper foil. Then, after 20 seconds, drop 170 ± 18 μL of chlorobenzene at the center of the film. Then, place the copper foil on a heating table and anneal it at 100 °C for 20 minutes to obtain a perovskite film / copper foil negative electrode sheet. Subsequently, use this as the negative electrode to prepare a half-cell.

[0046] Example 4:

[0047] The negative electrode material of this example has a halide perovskite structure of MAPbCl3, and the preparation steps are as follows:

[0048] 1. Dissolve 222.4 ± 10 mg of PbCl2 and 54 ± 10 mg of MACl in a mixed solvent of 800 ± 10 μL of DMF and 200 ± 10 μL of DMSO, and obtain a perovskite precursor solution with a concentration of 0.8 M through heating and stirring at 45 °C for 6.5 hours;

[0049] 2. After cleaning the copper foil with ethanol and drying it, use a slicer to cut it into circular electrodes with a diameter of 14 mm for later use. Take 50 μL of the above perovskite precursor solution and drop it on the surface of the copper foil. Then, after 20 seconds, drop 170±18 μL of chlorobenzene in the center of the film. Then, place the copper foil on a heating table and anneal it at 95°C for 20 minutes to obtain a perovskite film / copper foil negative electrode sheet, which is then used as the negative electrode to prepare a half-cell.

[0050] Embodiment 5:

[0051] The negative electrode material of this embodiment has a halide perovskite structure of MAPbCl3, and the preparation steps are as follows:

[0052] 1. Dissolve 278±10 mg PbCl2 and 67.5±10 mg MACl in 800±10 μL of DMF and 200±10 μL of DMSO mixed solvent, and heat and stir at 50°C for 6 hours to obtain a perovskite precursor solution with a concentration of 1.0 M;

[0053] 2. After cleaning and drying the copper foil with ethanol, use a slicer to cut it into circular electrodes with a diameter of 14 mm for later use. Take 50 μL of the above perovskite precursor solution and drop it on the surface of the copper foil. Then, after 20 seconds, drop 170±18 μL of chlorobenzene in the center of the film. Then, place the copper foil on a heating table and anneal it at 100°C for 20 minutes to obtain a perovskite film / copper foil negative electrode sheet, which is then used as the negative electrode to prepare a half-cell.

[0054] Embodiment 6:

[0055] The negative electrode material of this embodiment has a halide perovskite structure of MAPbCl3, and the preparation steps are as follows:

[0056] 1. Dissolve 333.6±10 mg PbCl2 and 81±10 mg MACl in 800±10 μL of DMF and 200±10 μL of DMSO mixed solvent, and heat and stir at 55°C for 5.5 hours to obtain a perovskite precursor solution with a concentration of 1.2 M;

[0057] 2. After cleaning the copper foil with ethanol and drying it, use a slicer to cut it into circular electrodes with a diameter of 14 mm for later use. Take 50 μL of the above perovskite precursor solution and drop it on the surface of the copper foil. Then, after 20 seconds, drop 170±18 μL of chlorobenzene in the center of the film. Then, place the copper foil on a heating table and anneal it at 105°C for 20 minutes to obtain a perovskite film / copper foil negative electrode sheet, which is then used as the negative electrode to prepare a half-cell.

[0058] Comparative Example 1:

[0059] The negative electrode material of this comparative example is a carbon-based negative electrode material, and the preparation steps are as follows:

[0060] 1. Add 80 wt.% of active material (conductive carbon powder), 10 wt.% of binder (polyvinylidene fluoride, PVDF), and 10 wt.% of conductive additive (super p) to an appropriate amount of N-methylpyrrolidone (NMP) solution. After sufficient ball milling, coat the cleaned and dried copper foil on a coater.

[0061] 2. Place the copper foil coated with the carbon negative electrode in a vacuum drying oven. First, evacuate the vacuum, and then dry it at 120 °C for 10 hours to obtain a carbon / copper foil negative electrode sheet. Subsequently, use this as the negative electrode to prepare a half-cell.

[0062] Detect the electrochemical properties of the negative electrode materials and their half-cells in Examples 1-3 and Comparative Example 1 above, as follows:

[0063] 1. Morphology and structure testing: Use a scanning electron microscope to test the microstructure of the negative electrode material, and use an X-ray diffractometer for crystal phase testing. Taking the MAPbI3 negative electrode material prepared in Example 2 as an example, its electron micrograph is as Figure 3 shown, showing that the MAPbI3 perovskite thin film completely covers the copper current collector, and the prepared MAPbI3 negative electrode material presents a dense thin film composed of granular and rod-shaped crystals; its XRD pattern is as Figure 4 shown, showing that the obtained material is the MAPbI3 perovskite phase, and it is determined that the material is the perovskite phase MAPbI3 with the ABX3 structure.

[0064] At the same time, the present invention deposits MAPbI3 with different lithium ion doping concentrations on FTO transparent conductive glass, and uses a scanning electron microscope to test its microstructure. The results are as Figure 1 、 2 shown. It can be seen from Figure 1 that when the molar doping concentration is less than 2%, the crystal grains and morphology of the perovskite thin film change little; when the molar doping concentration is greater than 5%, the crystal grains become larger; as the doping concentration reaches 10%, the crystal grains continue to increase, but holes appear in the thin film, indicating that the introduction of lithium ions affects the crystallization of perovskite. However, it can be seen from Figure 2 that even when the molar doping concentration reaches 10%, the prepared thin film still maintains the overall structure of perovskite, indicating that MAPbI3 perovskite has a very high concentration tolerance for lithium ions.

[0065] 2. Electrochemical performance test: To detect the performance of the anode material, a half-cell based on a lithium metal reference electrode was prepared and its electrochemical performance was tested and analyzed. In the constant current charge-discharge experiment of the battery test system, the charge-discharge voltage was limited to 0.01 - 3V. Taking the half-cell prepared in Example 2 as an example, the lithium-ion battery was cycled 200 times at a current density of 100 mA / g, and the capacity was stable at a relatively high specific capacity of 170 mAh / g. For details, please refer to Figure 9 . From Figure 9 , it can be seen that when MAPbI3 prepared in the present invention is used as the anode of a lithium-ion battery, it exhibits excellent cycle stability. After 270 consecutive charge-discharges, the performance does not decrease significantly. And from Figure 7 , 8 , it can be seen that when MAPbI3 prepared in the present invention is used as the anode of a lithium-ion battery, it exhibits excellent electrochemical cycle performance.

[0066] The electrochemical performances of the product materials and their half-cells obtained in Examples 1 - 3 and Comparative Example 1 are shown in Table 1 below.

[0067] Table 1 Electrochemical performance parameters of different lithium battery devices

[0068]

[0069] As an ionic crystal, the lattice structure of perovskite materials is relatively soft, resulting in lattice ions being easily activated by external factors such as light and voltage and departing from the lattice sites and migrating inside the crystal, thus leading to its electron and ion mixed conductivity characteristics. However, precisely because of this soft lattice structure of halide perovskite materials, they have a high tolerance for some foreign ions, such as lithium ions. Even high-concentration lithium-ion doping will not change their lattice structure. Moreover, due to the special octahedral lattice structure of perovskite materials, the lattice interstitial space is relatively large, enabling lithium ions to have a relatively large diffusion coefficient and diffusion rate in their lattice. And the halide perovskite lattice can accommodate an extremely high lithium-ion concentration, and during the process of lithium ions inserting and extracting from the halide perovskite anode, the perovskite crystal structure deforms very little. This indicates that halide perovskite as the anode material of a lithium-ion battery has very little volume change during charge-discharge, and at the same time has a relatively high capacity density. In addition, halide perovskite has excellent low-temperature solution self-assembly characteristics, with a simple preparation process and a low sintering temperature. These characteristics show that metal halide perovskite materials have great application potential in future low-cost, high-cycle-performance, and high-energy-density lithium-ion batteries.

[0070] Therefore, the present invention expands the selection space of the anode materials for lithium batteries. Compared with the traditional anode materials for lithium-ion batteries, the halide perovskite anode material for lithium-ion batteries of the present invention has stronger tolerance to lithium ions, and the preparation method is extremely simple, which is suitable for industrial production and commercial promotion and application.

[0071] It should be noted that the above embodiments are only the preferred embodiments of the present invention and do not limit the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, equivalent replacements or substitutions made on the basis of the above belong to the protection scope of the present invention.

Claims

1. A negative electrode material for a lithium ion battery, characterized in that: The negative electrode material has an ABX3 halide perovskite structure, wherein A is a monovalent organic cation, B is a divalent metal cation, and X is a halogen anion.

2. The negative electrode material according to claim 1, characterized in that: A is MA + or FA + ; The B is Pb 2+ or Sn 2+ ; X is Cl - Br - or I - .

3. The negative electrode material according to claim 1, characterized in that: The ABX3 is any one of MAPbI3, FAPbI3, MAPbBr3, FAPbBr3, MAPbCl3, and FAPbCl3.

4. The negative electrode material according to claim 3, characterized in that: The negative electrode material comprises a MAPbI3 film with a thickness of micrometer level.

5. A method for preparing a negative electrode material according to any one of claims 1 to 4, characterized in that Here are the steps: 1) Adding the halide perovskite precursor: BX2 and AX into the solvent according to the stoichiometric ratio, heating and stirring to obtain a halide perovskite precursor solution; 2) The halide perovskite precursor solution is deposited on a copper sheet current collector and annealed to obtain the negative electrode material.

6. The preparation method according to claim 5, characterized in that: The solvent is a mixed solvent of DMF and DMSO, and the mixed volume ratio of the two is 4:1±0.

01.

7. The preparation method according to claim 5, characterized in that: In step 1), the temperature during heating and stirring is 50±5° C. and the time is 6±0.5 h.

8. The preparation method according to claim 5, characterized in that: The concentration of the halide perovskite precursor solution in step 1) is 1.2±0.2M.

9. The preparation method according to claim 5, characterized in that: In step 2), the halide perovskite precursor solution is deposited on the copper sheet current collector by a wet film forming process such as drop coating, spin coating or blade coating, and the annealing temperature is 100±5°C.

10. A lithium ion battery, characterized in that A negative electrode material according to any one of claims 1 to 4.

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