Silicon composite negative electrode material and preparation method thereof
By forming a graphene oxide nanosheet coating layer on the surface of silicon-based materials and supplementing Li+ with lithium difluorophosphate, the problems of poor conductivity and volume expansion of silicon-based anode materials are solved, thereby improving the initial coulombic efficiency and cycle stability of lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- YICHUN GUOXUAN BATTERY CO LTD
- Filing Date
- 2023-05-24
- Publication Date
- 2026-07-03
AI Technical Summary
Silicon-based anode materials suffer from poor conductivity and volume expansion during charge and discharge, leading to electrode pulverization and SEI film rupture, which affects the lifespan of lithium-ion batteries and results in poor initial coulombic efficiency.
By reducing graphene oxide to graphene nanosheets and mixing them with silicon-based materials, a strong acid is used to oxidize them to form a graphene oxide nanosheet coating layer. Combined with the reaction of alumina and lithium hexafluorophosphate to generate lithium difluorophosphate, which provides Li+ replenishment, a uniform coating layer is formed to suppress volume expansion and improve conductivity.
It significantly improves the initial coulombic efficiency and cycle stability of silicon composite anode materials, thereby enhancing the charge-discharge efficiency and lifespan of batteries.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium-ion battery electrode materials technology, specifically to a silicon composite anode material and its preparation method. Background Technology
[0002] Climate change is a global problem facing humanity. With the surge in carbon dioxide emissions from various countries, greenhouse gases are increasing dramatically, threatening living systems. Against this backdrop, countries worldwide have reached global agreements to reduce greenhouse gas emissions, explicitly proposing to accelerate the optimization and adjustment of industrial and energy structures. The automotive industry is one of the major contributors to global greenhouse gas emissions, and with the continuous increase in my country's car ownership, reducing carbon emissions from the automotive sector is crucial. Therefore, the development of the new energy vehicle industry is essential and will inevitably experience rapid growth. This rapid development will also propel the lithium battery industry into a period of rapid growth.
[0003] Silicon-based materials, as novel anode materials for lithium-ion secondary batteries, exhibit higher specific capacity compared to graphite materials, and are also environmentally friendly, abundant, and low-cost. However, silicon anode materials suffer from poor conductivity during charge and discharge, and the insertion / extraction of Li... + The process involves significant volume expansion, causing the relevant electrodes to pulverize and peel off from the current collector, and the SEI film to continuously rupture and grow, consuming a large amount of Li. + This seriously affects the lifespan of lithium-ion batteries.
[0004] To address the problems associated with silicon-based materials, numerous researchers have employed techniques such as porosimetry and silicon alloying to significantly improve the electronic conductivity and volume expansion of silicon materials. However, their cycle performance and initial coulombic efficiency remain unsatisfactory. Therefore, optimizing silicon-based anode materials and developing anode materials with high specific capacity, high initial coulombic efficiency, and long cycle life has become an urgent problem to be solved in this field. Summary of the Invention
[0005] (a) Technical problems to be solved
[0006] To address the shortcomings of existing technologies, this invention provides a silicon composite anode material and its preparation method, which solves the problems of poor cycle performance and initial coulombic efficiency of silicon-based anode materials.
[0007] (II) Technical Solution
[0008] To achieve the above objectives, the present invention provides the following technical solution:
[0009] A method for preparing a silicon composite anode material includes the following steps:
[0010] (1) Graphene nanosheets were obtained by vacuum thermal reduction of graphene oxide;
[0011] (2) A strong acid is mixed with a silicon-based material, and the graphene nanosheets are added at the same time. After stirring for 5 min-60 min, a turbid liquid is obtained. The precipitate is obtained by filtration and washing.
[0012] (3) Lithium hexafluorophosphate is added to an organic solvent, and then placed in a sealed container. The precipitate and alumina are added at 60℃~180℃. After reacting for 2h~10h, the mixture is dried to obtain a silicon composite anode material.
[0013] Preferably, in step (2), the strong acid is at least one of concentrated sulfuric acid and concentrated nitric acid.
[0014] Preferably, in step (2), the mass ratio of graphene nanosheets to silicon-based materials is 0.5% to 5%.
[0015] Preferably, in step (2), the silicon-based material includes at least one of pure silicon, silicon suboxide, and carbon-coated silicon;
[0016] The carbon content in the carbon-coated silicon is less than 5%.
[0017] Preferably, in step (3), the organic solvent includes at least one of anhydrous ethanol, ethylene glycol, ethylene carbonate, diethyl carbonate, and dimethyl carbonate.
[0018] Preferably, in step (3), the mass ratio of lithium hexafluorophosphate to the precipitate is 1% to 5%.
[0019] Preferably, in step (3), the mass ratio of alumina to the precipitate is 0.5% to 2.5%.
[0020] Preferably, in step (1), the vacuum thermal reduction temperature is 100℃~2000℃ and the vacuum thermal reduction time is 5h~24h.
[0021] On the other hand, the present invention also provides a silicon composite anode material prepared by the preparation method described above, wherein the initial coulombic efficiency of the silicon composite anode material is 80.4% to 89.5%.
[0022] Preferably, the capacity retention rate of the silicon composite anode material after 100 cycles is 86.5% to 90.4%.
[0023] (III) Beneficial Effects
[0024] This invention provides a silicon composite anode material and its preparation method. Compared with the prior art, it has the following advantages:
[0025] 1. The present invention relates to a silicon composite anode material and its preparation method. A strong acid is used to oxidize the silicon-based material, forming an oxide layer on its surface. The oxide is primarily silicon oxide, which can alleviate the volume expansion effect of silicon. On the other hand, graphene nanosheets are obtained by reducing graphene oxide, and then oxidized with a strong acid to obtain graphene oxide nanosheets. The graphene oxide nanosheets are connected to the oxide layer on the silicon-based material surface via hydrogen bonds to form a coating layer. The nanoscale graphene oxide sheets can be uniformly dispersed on the silicon-based material surface, resulting in a more uniform coating layer. This further suppresses the volume expansion effect of silicon and improves the conductivity of the silicon-based material, thereby improving the initial coulombic efficiency and cycle stability of the silicon composite anode material.
[0026] 2. The silicon composite anode material and its preparation method of the present invention involve reacting alumina with lithium hexafluorophosphate to generate lithium difluorophosphate, which can provide Li... + Supplementing effective Li + This reduces the effective Li in the electrolyte and battery. + This reduces the consumption of energy and suppresses the increase in battery impedance, thereby improving the initial coulombic efficiency and cycle stability of silicon composite anode materials. Detailed Implementation
[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0028] This application provides a silicon composite anode material and its preparation method, which solves the problems of poor cycle performance and initial coulombic efficiency of silicon-based anode materials.
[0029] The technical solution in this application is to solve the above-mentioned technical problems, and the general idea is as follows:
[0030] This invention relates to a silicon composite anode material and its preparation method. A strong acid is used to oxidize the silicon-based material, forming an oxide layer on its surface, primarily silicon oxide. This oxide can alleviate the volume expansion effect of silicon. On the other hand, graphene nanosheets are obtained by reducing graphene oxide, and then oxidized with a strong acid to obtain graphene oxide nanosheets. The graphene oxide nanosheets are connected to the oxide layer on the silicon-based material surface via hydrogen bonds to form a coating layer. The nanoscale graphene oxide sheets can be uniformly dispersed on the silicon-based material surface, resulting in a more uniform coating layer. This further suppresses the volume expansion effect of silicon and improves the conductivity of the silicon-based material, thereby improving the initial coulombic efficiency and cycle stability of the silicon composite anode material.
[0031] The present invention relates to a silicon composite anode material and its preparation method, wherein lithium difluorophosphate is generated by reacting alumina with lithium hexafluorophosphate. Lithium difluorophosphate can provide Li+ to supplement effective Li+, thereby reducing the consumption of effective Li+ in the electrolyte and battery, and suppressing the increase of battery impedance, thereby improving the initial coulombic efficiency and cycle stability of the silicon composite anode material.
[0032] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods. Example 1
[0033] 10g of graphene oxide was weighed and placed in a tube furnace and evacuated to a vacuum. It was then sintered at a high temperature of 500℃ for 12 hours and cooled to room temperature to obtain thermally reduced graphene nanosheets.
[0034] Then, 20 mL of concentrated sulfuric acid and 20 g of pure silicon powder were measured and mixed, and 0.1 g of graphene nanosheets were added. After stirring for 20 min, a turbid liquid was obtained, which was then filtered, washed, and dried to obtain a precipitate.
[0035] Finally, 0.1g of lithium hexafluorophosphate was weighed and dissolved in 20mL of ethylene carbonate organic solvent. Then, it was placed in a sealed container and stirred at 100℃. 10g of the precipitate obtained above and 0.1g of alumina were added. After reacting for 4 hours, the mixture was dried to obtain a powder. After drying, a silicon composite anode material was obtained.
[0036] Example 2
[0037] 10g of graphene oxide was weighed and placed in a tube furnace and evacuated to a vacuum. It was then sintered at a high temperature of 500℃ for 12 hours and cooled to room temperature to obtain thermally reduced graphene nanosheets.
[0038] Then, 20 mL of concentrated sulfuric acid and 20 g of pure silicon powder were measured and mixed, and 0.2 g of graphene nanosheets were added. After stirring for 20 min, a turbid liquid was obtained, which was then filtered, washed, and dried to obtain a precipitate.
[0039] Finally, 0.1g of lithium hexafluorophosphate was weighed and dissolved in 20mL of ethylene carbonate organic solvent. Then, it was placed in a sealed container and stirred at 100℃. 10g of the precipitate obtained above and 0.1g of alumina were added. After reacting for 4 hours, the mixture was dried to obtain a powder. After drying, a silicon composite anode material was obtained.
[0040] Example 3
[0041] 10g of graphene oxide was weighed and placed in a tube furnace and evacuated to a vacuum. It was then sintered at a high temperature of 500℃ for 12 hours and cooled to room temperature to obtain thermally reduced graphene nanosheets.
[0042] Then, 20 mL of concentrated sulfuric acid and 20 g of pure silicon powder were measured and mixed, and 0.4 g of graphene nanosheets were added. After stirring for 20 min, a turbid liquid was obtained. The liquid was then filtered, washed, and dried to obtain a precipitate.
[0043] Finally, 0.1g of lithium hexafluorophosphate was weighed and dissolved in 20mL of ethylene carbonate organic solvent. Then, it was placed in a sealed container and stirred at 100℃. 10g of the precipitate obtained above and 0.1g of alumina were added. After reacting for 4 hours, the mixture was dried to obtain a powder. After drying, a silicon composite anode material was obtained.
[0044] Example 4
[0045] 10g of graphene oxide was weighed and placed in a tube furnace and evacuated to a vacuum. It was then sintered at a high temperature of 500℃ for 12 hours and cooled to room temperature to obtain thermally reduced graphene nanosheets.
[0046] Then, 20 mL of concentrated sulfuric acid and 20 g of silicon suboxide powder were weighed and stirred together. At the same time, 0.4 g of graphene nanosheets were added. After stirring for 10 min, a turbid liquid was obtained. After filtration, washing, and drying, a precipitate was obtained. Finally, 0.25 g of lithium hexafluorophosphate was weighed and dissolved in 20 mL of ethylene carbonate organic solvent. The solution was then placed in a sealed container and stirred at 100 °C. 10 g of the precipitate obtained above and 0.2 g of alumina were added. After reacting for 6 h, the solution was dried to obtain a powder. After drying, a silicon composite anode material was obtained.
[0047] Comparative Example 1
[0048] 10g of graphene oxide was weighed and placed in a tube furnace and evacuated to a vacuum. It was then sintered at a high temperature of 500℃ for 12 hours and cooled to room temperature to obtain thermally reduced graphene nanosheets.
[0049] Then, 20 mL of concentrated sulfuric acid and 20 g of pure silicon powder were measured and mixed, and 0.2 g of graphene nanosheets were added. After stirring for 20 min, a turbid liquid was obtained. After filtration, washing and drying, silicon composite anode material was obtained.
[0050] Comparative Example 2
[0051] This comparative example uses pure silicon anode material.
[0052] Comparative Example 3
[0053] This comparative example uses silicon suboxide as the anode material.
[0054] The negative electrode materials prepared in the above examples and comparative examples were mixed evenly in a mass ratio of negative electrode material: conductive carbon black (SP): carboxymethyl cellulose (CMC): styrene-butadiene rubber (SBR) = 96.3:0.8:1.3:1.6 to form a slurry. The slurry was then evenly coated onto the surface of copper foil and dried at 60°C for 0.5 h. It was then placed in a vacuum drying oven and dried at 120°C for 12 h. Finally, it was sliced to prepare a coin cell and subjected to charge-discharge cycle tests at 0.1C and 0.01–1.5V. The test results are shown in Table 1.
[0055] Table 1. Electrochemical performance test results of the prepared coin cells
[0056]
[0057] As shown in Table 1, firstly, compared with Comparative Examples 1-3, the silicon composite anode materials prepared in Examples 1-4 have significantly improved initial charge-discharge efficiency at 0.1C and specific capacity after 100 cycles. Therefore, the method of the present invention improves the initial coulombic efficiency and cycle stability of silicon composite anode materials.
[0058] Secondly, compared with the silicon composite anode material prepared in Comparative Example 1, the silicon composite anode material prepared in Example 2, when used to fabricate a coin cell, exhibits superior initial charge specific capacity, initial charge-discharge efficiency, specific charge capacity after 100 cycles, and capacity retention after 100 cycles compared to the coin cell prepared with the silicon composite anode material in Comparative Example 1. This may be because alumina reacts with lithium hexafluorophosphate to form lithium difluorophosphate, and lithium difluorophosphate can provide Li... + Supplementing effective Li + This reduces the effective Li in the electrolyte and battery. + This reduces the consumption of battery components and suppresses the increase in battery impedance, thereby improving the initial charge specific capacity, initial charge-discharge efficiency, charge specific capacity after 100 cycles, and capacity retention rate after 100 cycles of the coin cell.
[0059] Secondly, compared with the silicon composite anode material prepared in Example 4 and Comparative Example 3, the coin cell prepared using silicon suboxide as the anode material exhibited poor initial charge specific capacity, initial charge-discharge efficiency, specific charge capacity after 100 cycles, and capacity retention rate after 100 cycles. However, using the method of this invention, with the same silicon suboxide as the raw material, the silicon composite anode material prepared showed improved initial charge specific capacity, initial charge-discharge efficiency, specific charge capacity after 100 cycles, and capacity retention rate after 100 cycles. The improvement in initial charge-discharge efficiency, specific charge capacity after 100 cycles, and capacity retention rate after 100 cycles was particularly significant. This may be because the preparation method of this invention uses a strong acid to react with oxygen... Oxidation of silicon suboxide forms a silicon-based oxide layer on its surface, mitigating the volume expansion effect. Alternatively, graphene nanosheets are obtained by reducing graphene oxide, followed by oxidation with a strong acid to obtain graphene oxide nanosheets. These nanosheets are then bonded to the silicon-based material surface oxide via hydrogen bonds, forming a coating layer. The nanoscale graphene oxide sheets are uniformly dispersed on the silicon-based material surface, resulting in a more uniform coating layer, further suppressing the volume expansion effect of silicon suboxide and improving its conductivity. Additionally, alumina reacts with lithium hexafluorophosphate to generate lithium difluorophosphate, which can provide Li-. + Supplementing effective Li + This reduces the effective Li in the electrolyte and battery. + The consumption of silicon composite anode material is reduced, and the increase in battery impedance is suppressed, thereby improving the initial charge-discharge efficiency, the specific capacity after 100 cycles, and the capacity retention rate after 100 cycles of the coin cell prepared by silicon composite anode material, which in turn improves its initial coulombic efficiency and cycle stability.
[0060] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0061] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing a silicon composite anode material, characterized in that, Includes the following steps: (1) Graphene nanosheets were obtained by vacuum thermal reduction of graphene oxide; (2) A strong acid is mixed with a silicon-based material, and the graphene nanosheets are added at the same time. After stirring for 5 min-60 min, a turbid liquid is obtained. The precipitate is obtained by filtration and washing. (3) Lithium hexafluorophosphate is added to an organic solvent, and then placed in a sealed container. The precipitate and alumina are added at 60℃~180℃. After reacting for 2h~10h, the mixture is dried to obtain a silicon composite anode material.
2. The preparation method according to claim 1, characterized in that, In step (2), the strong acid is at least one of concentrated sulfuric acid and concentrated nitric acid.
3. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of graphene nanosheets to silicon-based materials is 0.5% to 5%.
4. The preparation method according to claim 1, characterized in that, In step (2), the silicon-based material includes at least one of pure silicon, silicon suboxide, and carbon-coated silicon; The carbon content in the carbon-coated silicon is less than 5%.
5. The preparation method according to claim 1, characterized in that, In step (3), the organic solvent includes at least one of anhydrous ethanol, ethylene glycol, ethylene carbonate, diethyl carbonate, and dimethyl carbonate.
6. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of lithium hexafluorophosphate to the precipitate is 1% to 5%.
7. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of alumina to the precipitate is 0.5% to 2.5%.
8. The preparation method according to claim 1, characterized in that, In step (1), the vacuum thermal reduction temperature is 100℃~2000℃ and the vacuum thermal reduction time is 5h~24h.
9. A silicon composite anode material prepared by the preparation method according to any one of claims 1-8, characterized in that, The initial coulombic efficiency of the silicon composite anode material is 80.4% to 89.5%.
10. The silicon composite anode material as described in claim 9, characterized in that, The capacity retention rate of the silicon composite anode material after 100 cycles is 86.5% to 90.4%.