Negative electrode material for improving cycle performance, preparation method of negative electrode material, negative electrode plate and battery

Abstract

The invention discloses a negative electrode material capable of improving cycle performance and a preparation method thereof, a negative electrode plate and a battery, and the preparation method comprises the following steps: S1, carrying out electrochemical etching on the surface of a silicon oxide material SiOx by using a copper-containing acidic etching agent to form a porous copper composite silicon oxide material; and S2, carrying out high-temperature calcination on the porous copper composite silica material and a conductive polymer to obtain the modified negative electrode material. The modified negative electrode material is prepared by adopting electrochemical etching and high-temperature calcination methods, so that the volume change of the material after long circulation can be relieved, the conductivity of the silica material is improved, the efficient charge transmission is ensured, and the integrity of an electrode is kept in the lithium intercalation and lithium removal processes, so that the cycle performance is remarkably improved.

Description

Technical Field

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

[0002] In the continuous development process of lithium-ion battery technology, the dominant position of graphite as a negative electrode material stems from its stable layered structure, which provides a reliable channel for the reversible insertion and extraction of lithium ions. At the same time, the balance between cycle performance and safety has been achieved through mature surface modification and electrolyte adaptation technologies. However, limited by the intrinsic characteristics of the material, its lithium storage capacity has approached the theoretical limit and it is difficult to break through the ceiling of high energy density requirements.

[0003] Silicon-oxygen materials have become the focus of research due to their lithium storage potential far exceeding that of traditional systems. Their unique composite structure of nano-silicon particles and oxidation matrix can theoretically alleviate volume expansion and maintain the continuity of the conductive network. However, there are still significant bottlenecks in practical applications: during the first charge and discharge, oxygen elements react with lithium to form an inert phase, resulting in irreversible consumption of some lithium; the repeated volume deformation of the silicon component during the lithiation process easily causes particle fragmentation and electrode structure deterioration, and at the same time, the continuous rupture and regeneration of the solid electrolyte interface (SEI) film on the surface further exacerbates capacity decay. Summary of the Invention

[0004] The present invention provides a negative electrode material, a preparation method thereof, a negative electrode sheet and a battery, aiming to improve the cycle performance through the modification of conventional negative electrode materials.

[0005] To achieve the above object, the technical solution provided by the present invention is as follows:

[0006] The first aspect of the present application provides a preparation method of a negative electrode material for improving cycle performance, including the following steps:

[0007] S1: Electrochemically etch the surface of silicon-oxygen material SiO x with a copper-containing acidic etchant to form a porous copper composite silicon-oxygen material;

[0008] S2: Calcinate the porous copper composite silicon-oxygen material and a conductive polymer at high temperature to obtain a modified negative electrode material.

[0009] To optimize the above technical solution, the specific measures taken further include:

[0010] The copper-containing acidic etchant used in the electrochemical etching in step S1 is a mixed solution of hydrofluoric acid and copper nitrate.

[0011] The preparation of the mixed solution of hydrofluoric acid and copper nitrate is to mix hydrofluoric acid with a concentration of 4 - 6 M and copper nitrate with a concentration of 0.008 - 0.012 M in a volume ratio of 2 - 4.5:1.

[0012] The electrochemical etching is carried out at a temperature of 50 - 70 °C, and the etching time is 5 - 7 h.

[0013] The high-temperature calcination of the porous copper composite silica material and the conductive polymer described in step S2 is carried out under the conditions of calcining at a temperature of 550 - 650 °C for 10 - 15 h, and an inert protective atmosphere is adopted during the process.

[0014] The conductive polymer is selected from one or a mixture of more of PPy (polypyrrole), PANI (polyaniline), and PTh (polythiophene).

[0015] The mass ratio of the porous copper composite silica material to the conductive polymer is 88 - 98:1.

[0016] The second aspect of the present application provides a negative electrode material for improving the cycle performance, and the negative electrode material is prepared by the above method.

[0017] The third aspect of the present application provides a negative electrode sheet, which includes the above negative electrode material for improving the cycle performance.

[0018] The fourth aspect of the present application provides a battery, which includes the above negative electrode sheet.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] The present invention prepares a modified negative electrode material by the methods of electrochemical etching and high-temperature calcination. The conventional silica (SiO x ) material is dissolved in hydrofluoric acid (HF) and copper nitrate solution to etch the surface of the SiO x material, and at the same time, Cu is deposited on its surface to form a porous copper composite silica material; the formation of the porous structure can relieve the volume change of the material after long cycling, and the deposition of Cu improves the conductivity of the SiO x material to a certain extent;

[0021] Then, the present invention calcines the porous copper composite silica material and the conductive polymer at high temperature. The coating of the conductive polymer can not only improve the conductivity of the silica material, but also the interface interaction ensures efficient charge transfer. At the same time, the introduction of the conductive polymer effectively reduces mechanical stress and maintains the integrity of the electrode during the repeated lithium insertion and deinsertion processes, thereby improving the cycle performance. Detailed Embodiments

[0022] The above content of the present invention will be further described in detail below in the form of specific embodiments. However, it should not be understood that the scope of the above subject matter of the present invention is limited to the following embodiments. Any technology implemented based on the above content of the present invention belongs to the scope of the present invention.

[0023] The experimental methods used in the following embodiments are all conventional methods unless otherwise specified. The reagents, methods and equipment used are all conventional reagents, methods and equipment in the technical field unless otherwise specified.

[0024] For the sake of brevity, only some numerical values and optional ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recorded; and any lower limit can be combined with other lower limits to form a range not explicitly recorded. Similarly, any upper limit can be combined with any other upper limit to form a range not explicitly recorded; the options in the optional range can also be combined arbitrarily.

[0025] The present invention provides a method for preparing a negative electrode material with improved cycle performance, comprising the following steps:

[0026] S1: Electrochemically etching the surface of silicon oxide material SiO x with a copper-containing acidic etching agent to form a porous copper composite silicon oxide material;

[0027] S2: High-temperature calcining the porous copper composite silicon oxide material with a conductive polymer to obtain a modified negative electrode material.

[0028] Through the synergistic modification strategy of electrochemically etching and composite coating with a conductive polymer, the present invention constructs a negative electrode material system with a stable structure and high-efficiency charge transport characteristics. During the material preparation process, a composite etching solution prepared from hydrofluoric acid and copper nitrate is first used to electrochemically treat the silicon oxide material. In this process, hydrofluoric acid controllably etches the surface of the silicon oxide particles, and simultaneously induces the copper ions in the copper nitrate solution to deposit on the material surface at the reduction potential, forming uniformly distributed copper nanoparticles. This step innovatively realizes the integrated process of etching to form pores and metal deposition. The generated three-dimensional porous framework significantly improves the adaptability of the material to volume expansion during charge and discharge. The introduction of copper nanoparticles not only enhances the matrix conductivity, but also the interfacial coupling effect between the copper nanoparticles and the silicon oxide matrix improves the structural stability of the material.

[0029] Subsequently, the conductive polymer is combined with the porous copper composite silicon oxide material through a high-temperature calcination process. Under the action of high temperature, the conductive polymer forms a continuous three-dimensional network coating layer, and its flexible molecular chains are tightly anchored on the surface of the silicon oxide particles through the dual actions of physical entanglement and chemical bonding. On the one hand, this composite structure constructs a fast charge transport channel throughout the electrode through the highly conductive polymer network, effectively reducing the interfacial impedance; on the other hand, the elastic characteristics of the polymer layer can form an adaptive buffer layer on the outer layer, absorbing mechanical stress through the dynamic deformation of molecular segments during the repeated insertion and extraction of lithium ions, and inhibiting the rupture and pulverization of active material particles. More importantly, the high-temperature treatment promotes the synergistic reconstruction of copper particles and the polymer carbon skeleton, forming a stable conductive-buffer dual-effect interface layer. This structure can maintain the structural integrity and electrical contact stability of the electrode material during long-term cycling, thereby significantly improving the capacity retention rate and cycle life of the battery.

[0030] The silicon oxide material of the present invention is conventional SiO x , where 0 < x < 2.

[0031] In some embodiments, the copper-containing acidic etchant used in the electrochemical etching in step S1 is a mixed solution of hydrofluoric acid and copper nitrate, and the mixed solution is prepared by mixing hydrofluoric acid with a concentration of 4 - 6M and copper nitrate with a concentration of 0.008 - 0.012M in a volume ratio of 2 - 4.5:1.

[0032] The electrochemical etching in step S1 is carried out at a temperature of 50 - 70°C for an etching time of 5 - 7h.

[0033] After electrochemical etching, the porous copper composite silicon oxide material is obtained through filtration, washing, and vacuum drying; among them, the solvents that can be used for washing are deionized water and alcohol; the conditions for vacuum drying are 60 - 70°C and 10 - 15h.

[0034] In step S2, the porous copper composite silicon oxide material and the conductive polymer are subjected to high-temperature calcination. The conditions for high-temperature calcination are calcination at a temperature of 550 - 650°C for 10 - 15h, and an inert protective atmosphere is used during the process.

[0035] Non-limiting examples of the conductive polymer of the present invention are selected from one or more mixtures of PPy (polypyrrole), PANI (polyaniline), and PTh (polythiophene);

[0036] The mass ratio of the porous copper composite silicon oxide material to the conductive polymer is 88 - 98:1.

[0037] In some embodiments, the high-temperature calcination is carried out in a tube furnace, and the porous copper composite silicon oxide material and the conductive polymer are mechanically mixed before calcination.

[0038] The present invention also provides a negative electrode material for improving cycle performance, which is prepared by the above method.

[0039] As a negative electrode active material, this negative electrode material is made into a negative electrode slurry by mixing with a conductive agent and a binder, and then coated on a negative electrode current collector. The proportions of the negative electrode active material, the conductive agent, and the binder can be obtained by those skilled in the art according to experience and in combination with the test process.

[0040] The present invention also provides a negative electrode sheet, which includes the above negative electrode material for improving cycle performance.

[0041] The present invention also provides a battery, which includes the above negative electrode sheet.

[0042] The battery containing the negative electrode material of the present application can be a lithium-ion battery, a sodium-ion battery, etc. Generally, the battery of the present application may include a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charge and discharge process of the battery, active ions are embedded and removed back and forth between the positive electrode sheet and the negative electrode sheet.

[0043] The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The present application does not have any special restrictions on the type of electrolyte, and it can be selected according to requirements.

[0044] The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent short circuit between the positive and negative electrodes, and at the same time allows ions to pass through. The present application does not have any special restrictions on the type of separator, and any well-known porous structure separator with good chemical stability and mechanical stability can be selected.

[0045] In some embodiments, the battery of the present application can be assembled into a battery module. The number of batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0046] The following further elaborates on the technical solution of the present invention with specific embodiments:

[0047] Example 1:

[0048] (1) Preparation of modified SiO x Material

[0049] Dissolve a certain amount of traditional SiO x material in 5M HF and 0.01M copper nitrate solution, stir evenly at 60 °C for 6 h, and obtain a porous copper composite silicon oxide material through filtration, washing, and vacuum drying; wherein, the volume ratio of HF to copper nitrate is 3 - 3.5:1;

[0050] The porous copper composite silica material and the conductive polymer PPy are mechanically mixed and then placed in a tubular furnace. Nitrogen is introduced, and calcination is carried out at a temperature of 600 °C for 12 h to obtain the modified SiO x material; wherein, the mass ratio of the porous copper composite silica material to the conductive polymer PPy is 92-94:1.

[0051] (2) Preparation of the negative electrode paste:

[0052] The negative electrode active material is the product modified SiO obtained in step 1 x material, the binder is LA132 (Indile), and the conductive agent is Super P (TIMCAL); they are stirred and mixed in a ratio of active material: binder: conductive agent = 8:1:1. After mixing evenly, it is coated on a 12-μm copper foil and dried in a vacuum drying oven at 120 °C for 12 h.

[0053] (3) Assembly of the button battery:

[0054] The button battery case is of the CR2032 model, the separator is a 20-μm separator, and the electrode sheet is a negative electrode sheet with a uniform coating. In a glove box filled with argon, the button battery is assembled in the order of battery case ~ placing the negative electrode sheet ~ dropping the electrolyte ~ placing the separator ~ dropping the electrolyte ~ placing the lithium sheet ~ placing the gasket spring sheet ~ battery case.

[0055] (4) Testing of the cycle performance:

[0056] The button battery is subjected to charge and discharge tests at 0.2C for 50 cycles and 100 cycles using a button battery charge and discharge tester (Wuhan Landian, CT2001A), and the voltage range is 0.01-3.0V. The test results are shown in the table.

[0057] Example 2:

[0058] It is basically the same as Example 1, except that the volume ratio of HF to copper nitrate is 2-2.5:1.

[0059] Example 3:

[0060] It is basically the same as Example 1, except that the volume ratio of HF to copper nitrate is 2.5-3:1.

[0061] Example 4:

[0062] It is basically the same as Example 1, except that the volume ratio of HF to copper nitrate is 3.5-4:1.

[0063] Example 5:

[0064] It is basically the same as Example 1, except that the volume ratio of HF to copper nitrate is 4-4.5:1.

[0065] Example 6:

[0066] Basically the same as Example 1, except that the mass ratio of the porous copper composite silicon oxide material to the conductive polymer PPy is 88-90:1.

[0067] Example 7:

[0068] Basically the same as Example 1, except that the mass ratio of the porous copper composite silicon oxide material to the conductive polymer PPy is 90-92:1.

[0069] Example 8:

[0070] Basically the same as Example 1, except that the mass ratio of the porous copper composite silicon oxide material to the conductive polymer PPy is 94-96:1.

[0071] Example 9:

[0072] Basically the same as Example 1, except that the mass ratio of the porous copper composite silicon oxide material to the conductive polymer PPy is 96-98:1.

[0073] Comparative Example 1:

[0074] The difference between this comparative example and Example 1 is that in step (1), there is no process of etching and depositing Cu, and the traditional SiO x material and the conductive polymer PPy are directly mechanically mixed and then calcined at the same conditions as in Example 1.

[0075] Comparative Example 2:

[0076] The difference between this comparative example and Example 1 is that in step (1), there is no introduction of the conductive polymer PPy, and the prepared porous copper composite silicon oxide material is directly calcined at the same conditions as in Example 1.

[0077] Comparative Example 3:

[0078] The difference between this comparative example and Example 1 is that the traditional SiO x material is directly used as the negative electrode material.

[0079] The cycle performance tests were carried out on each example and comparative example, and the test evaluation results are shown in Table 1; each of the above examples and comparative examples was repeated the experiment many times under the described conditions, and the data in Table 1 were the averages of multiple tests for each example.

[0080] Table 1 Cycle performance tests of each example and comparative example

[0081] Number 50-cycle performance 100-cycle performance Example 1 88.9％ 83.5％ Example 2 85.1％ 77.2％ Example 3 85.8％ 77.9％ Example 4 85.9％ 78.1％ Example 5 85.3％ 77.1％ Example 6 85.2％ 76.2％ Example 7 86.3％ 76.9％ Example 8 85.8％ 76.8％ Example 9 85.3％ 75.9％ Comparative Example 1 79.1％ 70.2％ Comparative Example 2 71.2％ 59.5％ Comparative Example 3 59.1％ 42.7％

[0082] By comparing Examples 1 to 6, it can be seen that the chemical composition of the etchant, i.e., the volume ratio of HF and copper nitrate, has a certain influence on the cycle performance of the modified negative electrode material obtained. By comparing Examples 1 and 7 to 9, it can be seen that the mass ratio of the porous copper composite silicon oxide material and the conductive polymer PPy also has a certain influence on the cycle performance of the modified negative electrode material obtained. After experimental verification, Example 1 is the optimal solution of the present invention.

[0083] Comparing Example 1 with Comparative Example 1, it can be seen that the performance of the negative electrode material will be significantly reduced without the process of etching and depositing Cu; Comparing Example 1 with Comparative Example 2, it can be seen that without the introduction of conductive polymer PPy, the porous copper composite silicon oxide material is directly calcined at high temperature under the same conditions, which has a relatively general improvement on the cycle performance of the negative electrode material, especially the 100-cycle cycle performance; Comparing Example 1 with Comparative Example 3, it can be seen that when the traditional SiO x When the material is used as a negative electrode material, the cycle performance data of the negative electrode material is far less than that of the embodiments, which verifies that the modification of the present application is relatively successful and has achieved significant technical effects.

[0084] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any technician familiar with the profession, without departing from the scope of the technical solution of the present invention, according to the technical essence of the present invention, any simple modification, equivalent replacement and improvement made to the above embodiment still falls within the protection scope of the technical solution of the present invention.

Claims

1. A preparation method of a negative electrode material for improving cycling performance, characterized in that, It includes the following steps: S1: Electrochemically etch the surface of silicon oxide material SiO x using a copper-containing acidic etchant to form a porous copper composite silicon oxide material; S2: High-temperature calcine the porous copper composite silicon oxide material and the conductive polymer to obtain a modified negative electrode material.

2. The method for preparing the anode material for improving cycle performance according to claim 1, characterized in that: The copper-containing acidic etchant used in the electrochemical etching in step S1 is a mixed solution of hydrofluoric acid and copper nitrate.

3. The method for preparing a negative electrode material for improving cycle performance according to claim 2, wherein: The mixed solution of hydrofluoric acid and copper nitrate is prepared by mixing hydrofluoric acid with a concentration of 4 - 6M and copper nitrate with a concentration of 0.008 - 0.012M in a volume ratio of 2 - 4.5:

1.

4. The method for preparing the anode material for improving cycle performance according to claim 1, characterized in that: The electrochemical etching is carried out at a temperature of 50 - 70°C, and the etching time is 5 - 7h.

5. The preparation method of the negative electrode material for improving cycle performance according to claim 1, characterized in that: In step S2, when the porous copper composite silicon oxide material and the conductive polymer are subjected to high-temperature calcination, the conditions for high-temperature calcination are calcining at a temperature of 550 - 650°C for 10 - 15h, and an inert protective atmosphere is used during the process.

6. The method for preparing a negative electrode material for improving cycle performance according to claim 1, wherein: The conductive polymer is selected from one or a mixture of more than one of PPy, PANI, and PTh.

7. The method for preparing a negative electrode material for improving cycle performance according to claim 1, characterized in that: The mass ratio of the porous copper composite silicon oxide material to the conductive polymer is 88 - 98:

1.

8. A negative electrode material for improving cycling performance, characterized in that: The negative electrode material is prepared by the method described in any one of claims 1 - 7.

9. A negative electrode sheet, characterized in that: It includes the negative electrode material for improving the cycle performance described in claim 8.

10. A battery, characterized in that: It includes the negative electrode sheet described in claim 9.