Magnesium-metal co-doped prelithiated silicon-oxygen composite and method of making

Abstract

The present application relates to a kind of magnesium-metal co-doped prelithiation silicon-oxygen composite material and its preparation method and lithium ion battery.The preparation method includes the following specific steps: providing micron silicon powder, silicon dioxide and magnesium powder are ball milled and mixed, and lithium carboxymethyl cellulose is added to vacuum high-temperature sintering, to obtain magnesium-doped silicon monoxide precursor;Magnesium-doped silicon monoxide precursor is added to the solution of 1-10wt% metal salt, filtration, vacuum drying, carbonization after drying, to obtain magnesium-metal co-doped silicon-oxygen material;Magnesium-metal co-doped silicon-oxygen material and prelithiation agent are mixed, and high-temperature sintering is carried out to obtain prelithiation silicon-oxygen material;Prelithiation silicon-oxygen material and organic reagent are mixed and coated, dried to obtain magnesium-metal co-doped prelithiation silicon-oxygen composite material.The present application provides a kind of magnesium-metal co-doped prelithiation silicon-oxygen composite material and lithium ion battery with good power performance and excellent cycle performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery materials, in particular to a magnesium-metal co-doped pre-lithiated silicon-oxygen composite material, a preparation method thereof and a lithium ion battery. BACKGROUND

[0002] At present, the research on silicon-based negative electrode materials mainly focuses on mixing silicon powder and carbon source materials by ball milling, and then pyrolyzing to obtain silicon monoxide, so as to reduce the expansion of the material and improve the electronic conductivity. However, this method still has problems of poor rate performance and low first charge-discharge efficiency.

[0003] In the prior art, pre-lithiated silicon-oxygen is prepared by chemical reaction of magnesium metal and lithium metal with silicon monoxide to improve the first charge-discharge efficiency of the material. However, this method may cause the power performance of the material to decrease, and gas is easily produced, which reduces the processing performance. In addition, this pre-lithiated silicon-oxygen needs to be prepared under high temperature conditions, the reaction conditions are harsh, the consistency is poor, and there is a power performance deviation.

[0004] Therefore, the prior art needs to be improved. SUMMARY

[0005] In the prior art, the method of preparing pre-lithiated silicon-oxygen by chemical reaction of magnesium metal and lithium metal still has deficiencies, and therefore the present application provides a magnesium-metal co-doped pre-lithiated silicon-oxygen composite material, a preparation method thereof and a lithium ion battery for solving the above problems.

[0006] In a first aspect, the present application provides a preparation method of a magnesium-metal co-doped pre-lithiated silicon-oxygen composite material, which comprises the following specific steps:

[0007] S1, micron silicon powder, silicon dioxide and magnesium powder are provided for ball milling and mixing, and carboxymethyl cellulose lithium is added for vacuum high-temperature sintering to obtain magnesium-doped silicon monoxide precursor;

[0008] S2, the magnesium-doped silicon monoxide precursor is added to a metal salt solution with a mass concentration of 1-10wt%, filtered, vacuum dried, and carbonized after drying to obtain a magnesium-metal co-doped silicon-oxygen material;

[0009] S3, the magnesium-metal co-doped silicon-oxygen material and a pre-lithiation agent are mixed and high-temperature sintered to obtain a pre-lithiated silicon-oxygen material;

[0010] S4, the pre-lithiated silicon-oxygen material and an organic reagent are mixed and coated, and dried to obtain a magnesium-metal co-doped pre-lithiated silicon-oxygen composite material.

[0011] In an implementation manner, in S1, the mass ratio of each raw material is silicon powder: silicon dioxide: magnesium powder: lithium carboxymethyl cellulose = (20-25):(40-50):(5-20):(10-20); the rotation speed of the ball milling is 500-1000 r / min, the ball milling time is 30-300 min; the vacuum high-temperature sintering temperature is 1500-2000℃, the sintering time is 1-6 h, and the vacuum environment is 1-20 Pa.

[0012] In an implementation manner, in S2, the mass ratio of the magnesium-doped silicon monoxide precursor and the metal salt is 100:(1-10); the carbonization time is 1-6 h, and the carbonization temperature is 1000-1300℃.

[0013] In an implementation manner, in S3, the mass ratio of the magnesium-metal co-doped silicon-oxygen material and the pre-lithiation reagent is 100:(10-20); in S3, the sintering temperature is 700-1000℃, and the sintering time is 1-6 h.

[0014] In an implementation manner, in S4, the mass ratio of the pre-lithiation silicon-oxygen material and the organic reagent is 100:(1-5).

[0015] In an implementation manner, in S2, the metal salt includes any one of silver acetate, silver oxalate, silver citrate, silver formate, silver acetate, silver propionate, silver acrylate and silver stearate, and the solvent is deionized water.

[0016] In an implementation manner, in S3, the pre-lithiation reagent includes any one of methyl lithium, ethyl lithium, isopropyl lithium, tert-butyl lithium, n-eicosyl lithium and phenyl lithium.

[0017] In an implementation manner, in S4, the organic reagent includes any one of acrylic acid-acrylamide copolymer, acrylic acid-acrylamide-acrylonitrile copolymer and acrylic acid-vinyl-2-hydroxyethanol-acrylamide copolymer.

[0018] In a second aspect, the application further provides a magnesium-metal co-doped pre-lithiation silicon-oxygen composite material, which is prepared by the above-mentioned method for preparing a magnesium-metal co-doped pre-lithiation silicon-oxygen composite material, and includes an inner core and an outer shell; the inner core is a magnesium-metal co-doped silicon-oxygen material, and the outer shell is an organic polymer coating layer, and the mass ratio of the outer shell is 1-5%.

[0019] In a third aspect, the application further provides a lithium ion battery, which uses the magnesium-metal co-doped pre-lithiation silicon-oxygen composite material as a negative electrode material.

[0020] Beneficial effects: the application improves the uniformity and stability of the material by ball milling mixing silicon powder, silicon dioxide and magnesium powder; the conductivity and stability of the silicon-oxygen material are increased by adding metal salt solution to form magnesium-metal co-doped silicon-oxygen material; the lithium ion conduction performance of the material is improved by adding pre-lithiation agent for high temperature sintering to form pre-lithiated silicon-oxygen material; the compatibility of the composite material with electrolyte is improved by coating the outer layer with organic compounds to form magnesium-metal co-doped pre-lithiated silicon-oxygen composite material co-doped with metal / magnesium, thereby improving the cycle stability, electrochemical performance and high temperature storage performance of the material, providing a simple preparation method, and at the same time providing a magnesium-metal co-doped pre-lithiated silicon-oxygen composite material and lithium ion battery with good power performance and excellent cycle performance. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a step flow chart of the preparation method of the magnesium-metal co-doped pre-lithiated silicon-oxygen composite material provided by the application.

[0022] Figure 2 is an SEM electron microscope image of the magnesium-metal co-doped pre-lithiated silicon-oxygen composite material provided by example 1.

[0023] The implementation, functional features and advantages of the application will be further described with reference to the drawings. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the application more clear, the application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the application and do not limit the application. In addition, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" described below means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the application. In this specification, the illustrative description of the above terms is not necessarily directed to the same embodiment or example. Moreover, the technical features involved in each embodiment of the application can be combined with each other as long as there is no conflict.

[0025] Please refer to Figure 1 , Figure 1 is a step flow chart of the preparation method of the magnesium-metal co-doped pre-lithiated silicon-oxygen composite material provided by the application.

[0026] The application provides a preparation method of a magnesium-metal co-doped pre-lithiated silicon-oxygen composite material, which comprises the following specific steps:

[0027] S1, micron silicon powder, silicon dioxide and magnesium powder are provided for ball milling mixing, and lithium carboxymethyl cellulose is added for vacuum high-temperature sintering to obtain a magnesium-doped silicon monoxide precursor;

[0028] S2, the magnesium-doped silicon monoxide precursor is added to a metal salt solution with a mass concentration of 1-10 wt%, filtered, vacuum dried, carbonized after drying to obtain a magnesium-metal co-doped silicon-oxygen material;

[0029] S3, the magnesium-metal co-doped silicon-oxygen material and a pre-lithiation agent are mixed and high-temperature sintered to obtain a pre-lithiated silicon-oxygen material;

[0030] S4, the pre-lithiated silicon-oxygen material and an organic reagent are mixed and coated, dried to obtain a magnesium-metal co-doped pre-lithiated silicon-oxygen composite material.

[0031] Specifically, in S1, the mass ratio of each raw material is silicon powder:silicon dioxide:magnesium powder: lithium carboxymethyl cellulose = (20-25):(40-50):(5-20):(10-20). The ball milling of the silicon powder, silicon dioxide and magnesium powder can improve the uniformity and stability of the material, the ball milling speed is 500-1000 r / min, and the ball milling time is 30-300 min. The mixed material is mixed with the lithium carboxymethyl cellulose, heated, and pressed into a block structure in a molten state, transferred to a vacuum sintering furnace for vacuum high-temperature sintering to generate silicon, silicon monoxide and magnesium silicate, and then the heating is stopped and cooled to obtain a magnesium-doped silicon monoxide precursor providing a stable structure. The lithium carboxymethyl cellulose can act as an electrolyte to play a role in ion transport, effectively improving the energy density, cycle life and safety performance of the lithium battery, thereby improving the overall performance of the lithium battery. Further, the vacuum high-temperature sintering temperature is 1500-2000℃, the sintering time is 1-6h, and the vacuum environment is 1-20Pa. In this step, magnesium-doped pre-lithiated silicon-oxygen is generated by reaction with organic lithium to improve the initial efficiency and power performance.

[0032] Specifically, in S2, the mass ratio of the magnesium-doped silicon monoxide precursor to the metal salt is 100:(1-10), the metal salt includes any one of silver acetate, silver oxalate, silver citrate, silver formate, silver acetate, silver propionate, silver acrylate and silver stearate, and the solvent is deionized water. Metal doping can improve the electronic conductivity of the composite material and improve its fast charging performance. This step also includes carbonization after drying, wherein the carbonization time is 1-6h and the carbonization temperature is 1000-1300℃. In this step, by adding a metal salt solution, a magnesium-metal co-doped silicon-oxygen material is formed, which increases the conductivity and stability of the silicon-oxygen material.

[0033] Specifically, in S3, the mass ratio of the magnesium-metal co-doped silicon-oxygen material and the pre-lithiation reagent is 100: (10-20), the pre-lithiation reagent includes a compound capable of decomposing elemental Li, and specifically, the pre-lithiation reagent includes any one of methyl lithium, ethyl lithium, isopropyl lithium, tert-butyl lithium, n-eicosyl lithium, and phenyl lithium. Further, the sintering temperature is 700-1000°C, and the sintering time is 1-6h. The high-temperature sintering is performed in an argon gas environment as a protective gas. In this step, the pre-lithiation agent is added to perform high-temperature sintering, thereby forming a pre-lithiated silicon-oxygen material and improving the lithium ion conductivity of the material.

[0034] In addition, by adding the metal salt in S2, the magnesium-metal co-doped silicon-oxygen material can reduce the pre-lithiation reaction speed, and the molten metal salt can effectively reduce the heat effect of the pre-lithiation process as a heat-absorbing medium, effectively slow down the rapid progress of the pre-lithiation reaction, effectively prevent the occurrence of local intense pre-lithiation reaction, effectively ensure the uniform and stable pre-lithiation process, solve the problem of uneven and rapid precipitation and growth of silicon grains due to uneven pre-lithiation, and further ensure excellent cycle performance on the basis of improving the initial efficiency.

[0035] Specifically, in S4, the mass ratio of the pre-lithiated silicon-oxygen material and the organic reagent is 100: (1-5). The organic reagent includes any one of acrylic acid-acrylamide copolymer, acrylic acid-acrylamide-acrylonitrile copolymer, and acrylic acid-vinyl-2-hydroxyethanol-acrylamide copolymer. In this step, the surface of the pre-lithiated silicon-oxygen material is coated with a polymer to reduce the gas production and reduce the contact with the electrolyte, thereby improving the storage performance.

[0036] The magnesium-metal co-doped pre-lithiated silicon-oxygen composite material prepared by the method of the present application includes an inner core and an outer shell. The inner core is a magnesium-metal co-doped silicon-oxygen material, and the outer shell is an organic polymer coating layer. The mass ratio of the outer shell is 1-5%. The magnesium content in the inner core is 1-5% by mass, and the metal content is 1-10wt%.

[0037] The technical solutions of the present application are further illustrated by the following examples.

[0038] Example 1

[0039] (1) 22g of micron silicon powder, 44g of silicon dioxide, and 10g of magnesium powder were added to a ball mill, and ball milling was performed at a rotation speed of 800r / min for 150min. The obtained material was mixed with 15g of lithium carboxymethyl cellulose, heated to 80°C, and pressed into a block structure in a molten state. Then, it was transferred to a vacuum sintering furnace, and reacted at a vacuum degree of 10Pa and a temperature of 1800°C for 3h. Then, the heating was stopped, and the material was cooled to obtain a magnesium-doped silicon monoxide precursor.

[0040] (2) 100 g of the magnesium-doped silicon monoxide precursor was added to 100 g of a 5 wt% silver acetate solution, filtered, vacuum dried at 80 °C for 24 h, and carbonized at 1200 °C for 3 h to obtain a magnesium-metal co-doped silicon-oxygen material;

[0041] (3) 100 g of the magnesium-metal co-doped silicon-oxygen material was uniformly mixed with 15 g of methyl lithium, sintered at 800 °C for 3 h to obtain a pre-lithiated silicon-oxygen material;

[0042] (4) 100 g of the pre-lithiated silicon-oxygen material was mixed and coated with 100 g of a 3 wt% acrylic acid-acrylamide copolymer cyclohexane solvent, vacuum dried at 100 °C for 24 h to obtain a magnesium-metal co-doped pre-lithiated silicon-oxygen composite material.

[0043] Example 2

[0044] (1) 20 g of micron silicon powder, 40 g of silicon dioxide, and 5 g of magnesium powder were added to a ball mill and ball milled at a rotation speed of 500 r / min for 300 min; then mixed with 10 g of lithium carboxymethyl cellulose, heated to 80 °C, and pressed into a block structure in a molten state; then transferred to a vacuum sintering furnace and reacted at a vacuum degree of 1 Pa and a temperature of 1500 °C for 1 h, and then the heating was stopped and cooled to obtain a magnesium-doped silicon monoxide precursor;

[0045] (2) 100 g of the magnesium-doped silicon monoxide precursor was added to 100 g of a 1 wt% silver oxalate aqueous solution, filtered, vacuum dried at 80 °C for 24 h, and carbonized at 1000 °C for 6 h to obtain a magnesium-metal co-doped silicon-oxygen material;

[0046] (3) 100 g of the magnesium-metal co-doped silicon-oxygen material was mixed with 10 g of ethyl lithium, sintered at 700 °C for 6 h to obtain a pre-lithiated silicon-oxygen material;

[0047] (4) 100 g of the pre-lithiated silicon-oxygen material was then mixed and coated with 100 g of a 1 wt% acrylic acid-acrylamide-acrylonitrile copolymer cyclohexane organic reagent, vacuum dried at 100 °C for 24 h to obtain a magnesium-metal co-doped pre-lithiated silicon-oxygen composite material.

[0048] Example 3

[0049] (1) 25 g micron silicon powder, 50 g silicon dioxide and 20 g magnesium powder were added into a ball mill and ball-milled at a rotation speed of 1000 r / min for 30 min; then the obtained material was mixed with 20 g lithium carboxymethyl cellulose, heated to 80°C, and pressed into a block structure in a molten state; then transferred into a vacuum sintering furnace, and reacted at a vacuum degree of 20 Pa and a temperature of 2000°C for 1 h, and then the heating was stopped and cooled to obtain a magnesium-doped silicon monoxide precursor;

[0050] (2) 100 g of the magnesium-doped silicon monoxide precursor was added into 100 g of a 10 wt% silver citrate solution, filtered, vacuum dried at 80°C for 24 h, carbonized at 1300°C for 1 h to obtain a magnesium-metal co-doped silicon-oxygen material;

[0051] (3) 100 g of the magnesium-metal co-doped silicon-oxygen material was mixed with 20 g of tert-butyllithium, sintered at 1000°C for 1 h to obtain a pre-lithiated silicon-oxygen material;

[0052] (4) 100 g of the pre-lithiated silicon-oxygen material was mixed with 100 g of a 5 wt% acrylic acid-vinyl-2-hydroxyethanol-acrylamide copolymer acetone solution for coating, vacuum dried at 100°C for 24 h to obtain a metal / magnesium co-doped pre-lithiated silicon-oxygen composite material.

[0053] Comparative Example 1:

[0054] Different from Example 1, no magnesium powder was added in step (1), and the others were the same as Example 1.

[0055] Comparative Example 2:

[0056] Different from Example 1, no organic reagent coating was performed, and the pre-lithiated silicon-oxygen material in step (3) was used as the negative electrode material, and the others were the same as Example 1.

[0057] Comparative Example 3:

[0058] Different from Example 1, no metal doping was performed, i.e., no silver acetate solution was added for doping, and the others were the same as Example 1.

[0059] Performance test:

[0060] (1) Morphology test

[0061] The magnesium-metal co-doped pre-lithiated silicon-oxygen composite material in Example 1 was subjected to SEM test, and the test results are shown in Figure 2 It can be seen from Figure 2 that the material presents a granular structure, and the material particle size distribution is uniform and reasonable, and the particle size is between 2-10 μm.

[0062] (2) Button cell test

[0063] The magnesium-metal co-doped pre-lithiated silicon-oxygen composite materials in Examples 1-3 and the silicon-oxygen composite materials in Comparative Examples 1-3 were assembled into button cells as lithium ion battery negative electrode materials, respectively denoted as A1, A2, A3, B1, B2, B3.

[0064] The specific preparation method is as follows: a binder, a conductive agent and a solvent are added to the lithium ion battery negative electrode material, stirring is performed to prepare a slurry, the slurry is coated on a copper foil, and a negative electrode sheet is prepared through drying and rolling; the binder used is LA132, the conductive agent is SP, and the solvent is NMP; the amount ratio of the negative electrode material, SP, PVDF and NMP is 95g:1g:4g:220mL; LiPF6 is used as an electrolyte in the electrolyte, and a mixture of EC and DEC in a volume ratio of 1:1 is used as a solvent; a lithium metal sheet is used as a counter electrode, and a polypropylene (PP) film is used as a separator.

[0065] The button cell assembly is performed in an argon-filled glove box. The electrochemical performance is tested on a Wuhan Lan Electric CT2001A battery tester, the charge and discharge voltage range is 0.005V to 2.0V, the charge and discharge rate is 0.1C, and the full charge expansion of the negative electrode sheet is tested at the same time. The tap density and specific surface area of the material are tested according to GB / T-38823-2020 “Silicon Carbon”; and the powder conductivity is tested by a four-probe tester, and the results are shown in Table 1.

[0066] Table 1, button cell test results of each group of materials

[0067]

[0068] As can be seen from the data in Table 1, the specific capacity and the first efficiency of the magnesium-metal co-doped pre-lithiated silicon-oxygen composite material prepared by the examples of the present application are obviously better than those of the comparative examples. In the preparation method of the present application, magnesium is doped in silicon monoxide to form magnesium silicate to reduce the irreversible capacity and improve the first efficiency, at the same time, silicon monoxide reacts with organic lithium to generate magnesium-doped pre-lithiated silicon-oxygen, which improves the first efficiency and reduces the polarization of the material, improves the specific capacity of the material, and the outer shell is coated with an organic reagent to constrain the expansion of the silicon-based material during the charge and discharge process, and improves the tap density of the material.

[0069] (3) Soft package battery test:

[0070] The magnesium-metal co-doped pre-lithiated silicon-oxygen composite materials in Examples 1-3 and Comparative Examples 1-3 were doped with 90% artificial graphite as a negative electrode material to prepare a negative electrode sheet, NCM532 was used as a positive electrode material; LiPF6 was used as an electrolyte in an electrolyte, and a mixture of EC and DEC in a volume ratio of 1:1 was used as a solvent; Celgard 2400 film was used as a separator to prepare 5Ah soft package batteries, labeled as C1, C2, C3, D1, D2, and D3. The liquid absorption and retention capacity of the negative electrode sheet, the electrode sheet rebound rate, the cycle performance, and the rate performance were tested respectively.

[0071] a. Liquid absorption test

[0072] A 1 mL burette was used to take 1 mL of electrolyte, and one drop was added to the surface of the electrode sheet, and the time was counted until the electrolyte was completely absorbed, and the time t was recorded. The test results are shown in Table 2.

[0073] b. Liquid retention rate test

[0074] The theoretical liquid absorption amount m1 of the electrode sheet was calculated according to the electrode sheet parameters, and the weight m2 of the electrode sheet was measured. Then the electrode sheet was placed in the electrolyte for 24h, and the weight of the electrode sheet was measured as m3, the liquid absorption amount of the electrode sheet m3-m2 was calculated, and the liquid retention rate was calculated according to the following formula: liquid retention rate = (m3-m2)*100% / m1. The test results are shown in Table 2.

[0075] Table 2, soft package battery test results of each group of materials

[0076]

[0077] As can be seen from Table 2, the liquid absorption and retention capacity of the magnesium-metal co-doped pre-lithiated silicon-oxygen composite material obtained in Examples 1-3 is significantly higher than that of the comparative examples. The experimental results show that the magnesium-metal co-doped pre-lithiated silicon-oxygen composite material prepared by the present application has a high specific surface area, which can improve the liquid absorption and retention capacity of the material.

[0078] c. Electrode sheet rebound rate test

[0079] First, the average thickness of the electrode sheet was tested by a thickness gauge, which was D1, then the electrode sheet was placed in a vacuum drying oven at 80℃ for 48h, the thickness of the electrode sheet was tested, which was D2, and the rebound rate was calculated according to the following formula: rebound rate = (D2-D1)*100% / D1. The test results are shown in Table 3.

[0080] d. Electrode sheet resistivity test

[0081] The resistivity of the electrode sheet was tested by a resistivity tester, and the test results are shown in Table 3.

[0082] Table 3, electrode sheet rebound rate test and electrode sheet resistivity test results of each group of materials

[0083]

[0084] As can be seen from the data in Table 3, the negative electrode sheet rebound rate and resistivity of the magnesium-metal co-doped pre-lithiated silicon-oxygen composite material obtained in Examples 1-3 are significantly lower than those of Comparative Examples 1-3. The experimental results show that the magnesium and its shell-coated metal compound with high electron conductivity in the material of the examples improve the powder conductivity of the material and improve the resistivity of the electrode sheet.

[0085] e. Cycle performance test

[0086] The cycle performance of the battery was tested at a charge-discharge rate of 1C / 1C and a voltage range of 2.5V-4.2V at a temperature of 25±3℃. The test results are shown in Table 4.

[0087] f. Rate performance

[0088] The soft pack battery of Examples 1-3 and Comparative Examples 1-3 was charged to 4.2C in a constant current+constant voltage mode of 0.1C+0.01C, and the constant current ratio of the material = constant current capacity / (constant current capacity+constant voltage capacity) was calculated. The test results are shown in Table 4.

[0089] Table 4, cycle performance test and rate performance test results of each group of materials

[0090]

[0091] As can be seen from Table 4, the cycle performance of the battery prepared from the magnesium-metal co-doped pre-lithiated silicon-oxygen composite material of the application is significantly better than that of the comparative examples. The experimental results show that the electrode sheet prepared from the composite material has a lower expansion rate and excellent liquid absorption and liquid retention capacity, which reduces the expansion during the charge-discharge process and improves the cycle performance. At the same time, the electrode sheet of the material of the examples has a lower resistivity, which improves the constant current ratio of the material during the charge-discharge process and improves the rate performance.

[0092] In summary, the application improves the uniformity and stability of the material by ball milling silicon powder, silicon dioxide and magnesium powder; increases the conductivity and stability of the silicon-oxygen material by adding a metal salt solution to form a magnesium-metal co-doped silicon-oxygen material; improves the lithium ion conductivity of the material by adding a pre-lithiation agent for high temperature sintering to form a pre-lithiated silicon-oxygen material; improves the cycle stability, electrochemical performance and high temperature storage performance of the material by coating the outer layer with an organic compound to form a magnesium-metal co-doped pre-lithiated silicon-oxygen composite material co-doped with metal / magnesium, and provides a simple preparation method, as well as a magnesium-metal co-doped pre-lithiated silicon-oxygen composite material and a lithium ion battery with good power performance and excellent cycle performance.

[0093] The above merely describes preferred embodiments of the present application, and is not intended to limit the patent scope of the present application, and any equivalent structure or equivalent process conversion made by using the content of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for preparing a magnesium-metal co-doped prelithiated silicon-oxygen composite material, characterized in that, The method comprises the following specific steps: S1, providing micron silicon powder, silicon dioxide and magnesium powder for ball milling mixing, and adding lithium carboxymethyl cellulose for vacuum high-temperature sintering to obtain a magnesium-doped silicon monoxide precursor; S2, adding the magnesium-doped silicon monoxide precursor to a metal salt solution with a mass concentration of 1-10 wt%, filtering, vacuum drying, and carbonizing after drying to obtain a magnesium-metal co-doped silicon-oxygen material; S3, mixing the magnesium-metal co-doped silicon-oxygen material and a prelithiation agent, and high-temperature sintering to obtain a prelithiated silicon-oxygen material; S4, mixing and coating the prelithiated silicon-oxygen material and an organic reagent, and drying to obtain a magnesium-metal co-doped prelithiated silicon-oxygen composite material; In S1, the mass ratio of each raw material is silicon powder:silicon dioxide:magnesium powder:lithium carboxymethyl cellulose=(20-25):(40-50):(5-20):(10-20); the rotation speed of the ball milling mixing is 500-1000 r / min, and the ball milling mixing time is 30-300 min; the vacuum high-temperature sintering temperature is 1500-2000℃, the sintering time is 1-6 h, and the vacuum environment is 1-20 Pa; In S2, the mass ratio of the magnesium-doped silicon monoxide precursor and the metal salt is 100:(1-10); the carbonization time is 1-6 h, and the carbonization temperature is 1000-1300℃; In S3, the mass ratio of the magnesium-metal co-doped silicon-oxygen material and the prelithiation agent is 100:(10-20); in S3, the sintering temperature is 700-1000℃, and the sintering time is 1-6 h; In S3, the prelithiation agent comprises any one of methyl lithium, ethyl lithium, isopropyl lithium, tert-butyl lithium, n-eicosyl lithium and phenyl lithium; In S2, the metal salt comprises any one of silver acetate, silver oxalate and silver citrate, and the solvent is deionized water; In S4, the organic reagent comprises any one of acrylic acid-acrylamide copolymer, acrylic acid-acrylamide-acrylonitrile copolymer and acrylic acid-vinyl-2-hydroxyethanol-acrylamide copolymer; In S4, the mass ratio of the prelithiated silicon-oxygen material and the organic reagent is 100:(1-5); The magnesium-metal co-doped prelithiated silicon-oxygen composite material comprises a core and a shell, the core is the magnesium-metal co-doped silicon-oxygen material, and the shell is an organic polymer coating layer, and the mass percentage of the shell is 1-5%.

2. A magnesium-metal co-doped prelithiated silicon-oxygen composite material, characterized in that, The magnesium-metal co-doped prelithiated silicon-oxygen composite material is prepared by the method in claim 1.

3. A lithium-ion battery, characterized by, The magnesium-metal co-doped prelithiated silicon-oxygen composite material in claim 2 is used as a negative electrode material.

Images