Negative electrode material, lithium ion battery containing negative electrode material and preparation method of negative electrode material
By designing a multi-layer coating structure, the problems of expansion, conductivity, and lithium conductivity of silicon-based anode materials were solved, improving the overall performance and process stability of the battery and realizing the efficient application of silicon-based anode materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-25
- Publication Date
- 2026-03-31
AI Technical Summary
Existing silicon-based anode materials suffer from problems such as expansion, conductivity, lithium conductivity, and dispersion uniformity during use, making it difficult to meet the diverse requirements of complex systems. Furthermore, existing coating modification methods are difficult to balance process stability.
The system employs a multi-layer coating structure, including a core, a first coating layer, a second coating layer, and a third coating layer. The core is a porous carbon matrix and silicon particles, the first coating layer is amorphous carbon, the second coating layer is an elastic polymer layer and metal oxide, and the third coating layer is graphite microcrystals and amorphous carbon. The non-continuous and continuous coating forms a uniform distribution, ensuring the uniformity of the metal oxide and graphite microcrystals.
It effectively suppressed the expansion problem, improved conductivity and lithium conductivity, enhanced the overall performance of the battery such as fast charging performance, rate performance and cycle performance, and ensured process stability and uniform dispersion of graphite microcrystals.
Smart Images
Figure CN121769042A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a negative electrode material, a lithium-ion battery containing the same, and a method for preparing the same. Background Technology
[0002] Currently, the market penetration rate of silicon-based anodes is increasing year by year and is expected to exceed 10%. This is mainly due to the advantages of silicon-based materials, such as high specific energy and high potential. However, the low conductivity and high expansion are still limiting factors restricting the explosive growth of silicon-based materials. This requires researchers to develop silicon-based materials that meet different requirements for different application scenarios. Among them, expansion, conductivity, and lithium conductivity are important intrinsic problems that urgently need to be solved. Current research mainly falls into the following categories: ① Porous carbon is used to expand pores and increase mesoporosity, thereby reducing expansion, but there are problems with process stability and product consistency; ② Graphene / CNT doping is used to relieve stress, improve matrix strength, and simultaneously optimize electron conduction, but there are dispersion problems. If the dispersion does not meet the requirements, the performance will deteriorate.
[0003] From an industrialization perspective, surface coating is the route that best meets the requirements of process stability, product uniformity, and high marketability. Based on this, existing technologies mostly start with surface coating modification. However, single modification is still insufficient to meet the diverse requirements of complex systems. Synergistic effects are still needed to address the constraints on product performance and marketability. Summary of the Invention
[0004] To address the shortcomings of existing coating modification methods in simultaneously addressing the expansion, conductivity, lithium conductivity, dispersion uniformity, and process stability of anode materials, this invention provides an anode material, a lithium-ion battery containing the anode material, and a method for preparing the same. This anode material, based on a multi-layer coating structure, effectively suppresses expansion during use while simultaneously improving conductivity and lithium conductivity. When used in a battery, it effectively improves the overall performance of the resulting battery, such as fast-charging performance, rate performance, and cycle performance. Furthermore, this preparation method ensures dispersion uniformity and process stability during the coating process.
[0005] To achieve the above objectives, the present invention adopts the following technical solution.
[0006] This invention provides a negative electrode material, which comprises, from the inside out, the following structure: a core, a first coating layer, a second coating layer, and a third coating layer; wherein,
[0007] The core comprises a porous carbon matrix and silicon particles deposited within the pores of the porous carbon matrix;
[0008] The first coating layer comprises amorphous carbon;
[0009] The second coating layer includes an elastic polymer layer and a metal oxide, wherein the elastic polymer layer exists in a three-dimensional cyclic structure, and the metal oxide is uniformly distributed on the surface of the elastic polymer layer;
[0010] The third coating layer comprises graphite microcrystals and amorphous carbon, wherein the graphite microcrystals are uniformly distributed within the amorphous carbon.
[0011] In this invention, based on the pore structure of the porous carbon matrix, the amorphous carbon in the first coating layer is coated on the surface of the porous carbon matrix in a discontinuous manner, that is, some of the amorphous carbon is located in the pores of the porous carbon matrix; in the second coating layer, the elastic polymer layer is uniformly coated on the surface of the first coating layer in a three-dimensional cyclic structure, forming a continuous coating structure, and the surface of the elastic polymer layer (i.e., between the elastic polymer layer and the third coating layer) is uniformly distributed with metal oxides; correspondingly, the amorphous carbon in the third coating layer is coated on the surface of the second coating layer in a continuous manner, and graphite microcrystals are uniformly distributed therein.
[0012] The meaning of "uniform distribution" is that, on the surface of the elastic polymer layer of the second coating layer, the metal oxides do not form an aggregate structure; and in the amorphous carbon of the third coating layer, the graphite microcrystals do not form an aggregate structure.
[0013] In some embodiments, the silicon content of the negative electrode material is 40wt%-60wt%, for example 47.6wt%.
[0014] In some embodiments, the carbon content of the negative electrode material is 40wt%-60wt%, for example, 47.3wt%. The carbon content is the sum of the carbon content in the first coating layer and the third coating layer.
[0015] In some embodiments, the elastic polymer includes one or more of polyacrylonitrile (PAN), polyaniline, polyvinyl alcohol, polyimide, polyurethane and their corresponding derivatives, such as polyacrylonitrile and / or polyimide.
[0016] In some embodiments, the content of the elastic polymer in the negative electrode material is 0.1-5 wt%, for example 1.5 wt%.
[0017] In some embodiments, the metal oxide includes transition metal oxides, preferably one or more oxides of Fe, Cu, Co and Ni, such as one or more of ferrous oxide, iron oxide, magnetite, cuprous oxide, copper oxide, cobalt oxide, cobalt oxide, nickel oxide and nickel oxide.
[0018] In some embodiments, the content of the metal oxide in the negative electrode material is 0.1wt%-10wt%, for example 0.5wt%.
[0019] In some implementations, the thickness of the first coating layer is 5-15 nm.
[0020] In some implementations, the thickness of the second coating layer is 1-5 nm.
[0021] In some implementations, the thickness of the third coating layer is 5-35 nm.
[0022] The present invention also provides a method for preparing a negative electrode material, the method comprising the following steps:
[0023] S1. The core material is obtained by carbon deposition using the first deposition gas to obtain the first precursor.
[0024] The core material includes a porous carbon matrix and silicon particles deposited in the pores of the porous carbon matrix, and the first deposition gas includes a first carbon source gas.
[0025] S2. A mixed solution containing the first precursor, a metal source, and a polymer is preheated and then heat-treated to obtain a second precursor.
[0026] The temperature of the preheating treatment is lower than the temperature of the heat treatment.
[0027] S3. The second precursor is subjected to secondary carbon deposition using a second deposition gas to obtain the negative electrode material.
[0028] The second deposition gas includes a second carbon source gas.
[0029] In this invention, a multilayered anode material can be prepared through the above steps. In step S1, the core material undergoes almost no change in physicochemical properties throughout the process, but after carbon deposition, amorphous carbon forms on its surface, creating numerous grafting sites. In step S2, in the mixed solution, the metal from the metal source gradually bonds with the polymer in ionic form, and gradually coats the surface of the first precursor through the grafting sites between the polymer and the core material. Preheating accelerates the self-polymerization reaction of the polymer, thereby speeding up bonding and coating. During further heat treatment, metal ions gradually form metal oxides, catalyzing the dehydrogenation reaction of the polymer, thus forming a three-dimensional cyclic structure (i.e., an elastic polymer layer) coating the surface of the first precursor. At this point, the metal oxide exists on the surface of the elastic polymer layer. Finally, in step S3, during the carbon deposition process, the carbon source gas first forms amorphous carbon, and then, under the catalysis of the metal oxide, some carbon precipitates to form graphite microcrystals, gradually forming non-oriented graphite microcrystals. The cyclization structure formed by the polymer in step S2 ensures the uniform distribution of metal oxides, thereby ensuring the uniform distribution of graphite crystals.
[0030] In this invention, in step S1, the preparation of the core material can be carried out according to conventional operating conditions in the art.
[0031] In some implementations, step S1, the preparation of the core material includes the following steps:
[0032] The porous carbon matrix is prepared by silicon deposition using a third deposition gas; wherein the third deposition gas contains a silicon source gas.
[0033] The silicon source gas can be conventional in the art, such as silane.
[0034] In this case, based on 1 kg of the porous carbon matrix, the gas flow rate of the silicon source gas can be 1-5 L / min, for example 2 L / min.
[0035] The third deposition gas may also include an inert gas; the inert gas may include, for example, nitrogen; the volume ratio of the silicon source gas to the inert gas may be (1-3):5, for example, 1:5.
[0036] The silicon deposition temperature is preferably 500-600°C, for example 550°C.
[0037] The silicon deposition time is preferably 300-500 min, for example 400 min.
[0038] In this invention, the silicon deposition step may include a heating step, i.e., silicon deposition begins when the temperature is raised to a holding temperature; the silicon deposition temperature refers to the holding temperature. Those skilled in the art will understand its specific meaning.
[0039] The heating rate before silicon deposition can be 2-10℃ / min, for example 5℃ / min.
[0040] The process may further include a step of purging with an inert gas for displacement before silicon deposition.
[0041] In this invention, in step S1, the first carbon source gas can be conventional in the art, such as acetylene.
[0042] In some implementations, in step S1, the gas flow rate of the first carbon source gas can be 1-5 L / min, for example, 2 L / min, based on 1 kg of the porous carbon matrix.
[0043] In some embodiments, in step S1, the first deposition gas may further include an inert gas; the inert gas includes, for example, nitrogen; the volume ratio of the first carbon source gas to the inert gas may be (1-3):5, for example, 1:5.
[0044] The temperature of the primary carbon deposition is preferably 500-600°C, for example 550°C.
[0045] The carbon deposition time for a single deposition is preferably 30-50 minutes, for example, 40 minutes.
[0046] The process includes a cooling step after the initial carbon deposition, with a cooling rate of 1-5°C / min, for example, 2°C / min.
[0047] In some implementations, in step S2, the metal source includes a transition metal salt.
[0048] The transition metal salt preferably includes one or more of Fe salt, Cu salt, Co salt and Ni salt.
[0049] The transition metal salt preferably includes one or more of nitrates, sulfates, and chlorides.
[0050] Specifically, the metal source may be ferric nitrate and / or ferric chloride.
[0051] In some implementations, in step S2, the mass ratio of the metal source to the first precursor is 0.1%-5%, for example 0.5%, 1% or 1.5%.
[0052] In some embodiments, in step S2, the polymer includes one or more of polyacrylonitrile (PAN), polyaniline, polyvinyl alcohol, polyimide, polyurethane and their corresponding derivatives, such as polyacrylonitrile and / or polyimide.
[0053] In some implementations, in step S2, the mass ratio of the polymer to the first precursor is 0.1%-10%, for example 1%, 2% or 3%.
[0054] In some embodiments, step S2, the preparation of the mixed solution includes the following steps:
[0055] I. The first precursor is mixed with water to obtain a first mixture;
[0056] II. The polymer and the metal source are mixed to obtain a second mixture;
[0057] III. The second mixture is added to the first mixture in batches and mixed thoroughly to obtain the final product.
[0058] In step I, the mixing is performed, for example, by stirring at 1000 rpm for 2 hours.
[0059] In step II, the mixing is performed, for example, by stirring at 2000 rpm for 2 hours.
[0060] In step II, the mixing is performed, for example, at 800 rpm.
[0061] In step III, the addition in batches is preferably done in three equal batches.
[0062] In some implementations, the temperature of the preheating treatment in step S2 is 40-50°C, for example, 45°C.
[0063] In some implementations, the preheating treatment in step S2 takes 1-3 hours, for example, 2 hours.
[0064] In some implementations, step S2 further includes a solid-liquid separation process to obtain a solid and a drying process after the preheating treatment.
[0065] The solid-liquid separation is preferably carried out by pressure filtration.
[0066] The drying process is preferably carried out using a VC dryer.
[0067] The drying process, for example, involves drying at 120°C for 6 hours.
[0068] In some implementations, in step S2, the temperature of the heat treatment is 100-400°C, for example 250°C or 280°C.
[0069] In some implementations, the heat treatment time in step S2 is 4-8 hours, for example, 6 hours.
[0070] In some embodiments, in step S2, the heat treatment is carried out under inert conditions; the inert gas is preferably one or more of nitrogen, argon and helium, for example, nitrogen.
[0071] In some embodiments, step S2 further includes a cooling step after the heat treatment; the cooling rate is preferably 1-5°C / min, for example 2°C / min.
[0072] In this invention, in step S3, the second carbon source gas can be conventional in the art, such as acetylene.
[0073] In some implementations, in step S3, the gas flow rate of the carbon source gas is 1-10 L / min, for example, 3 L / min, 5 L / min or 8 L / min, based on 2 kg of the first precursor.
[0074] In some embodiments, in step S3, the second deposition gas further includes an inert gas.
[0075] The inert gas preferably includes nitrogen.
[0076] The volume ratio of the carbon source gas to the inert gas is preferably (1-10):15, for example, 3:15, 5:15 or 8:15.
[0077] In some implementations, in step S3, the temperature of the secondary carbon deposition is 200-600°C, for example 450°C, 550°C or 600°C.
[0078] In some implementations, the secondary carbon deposition time in step S3 is 4-8 hours, for example, 6 hours.
[0079] In some implementations, in step S3, the secondary carbon deposition is carried out in a fluidized bed.
[0080] In some implementations, step S3 further includes washing and drying steps after the secondary carbon deposition.
[0081] The washing process preferably includes washing with water and acid alternately, for example, washing with water, acid and water in sequence; the solid-liquid ratio of the washing process is, for example, 1:2 (w / w); the acid is, for example, hydrochloric acid, and the concentration of the hydrochloric acid is, for example, 0.5 mol / L.
[0082] The present invention also provides a negative electrode material, which is prepared by the method for preparing negative electrode materials as described above.
[0083] In some implementations, the negative electrode material is as defined above.
[0084] The present invention also provides a lithium-ion battery comprising the negative electrode material as described above.
[0085] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.
[0086] The reagents and raw materials used in this invention are all commercially available.
[0087] The positive and progressive effects of this invention are as follows:
[0088] The negative electrode material of this invention, based on a multilayer structure of "porous carbon / silicon matrix - carbon coating layer - elastic polymer coordination metal layer - carbon coating layer containing graphite microcrystals", effectively suppresses the expansion problem during use and improves conductivity and lithium conductivity at the same time. When used in batteries, it can effectively improve the overall performance of the resulting batteries, such as fast charging performance, rate performance and cycle performance. Moreover, the preparation method can also ensure the uniformity of graphite microcrystal dispersion and process stability during the coating process. Attached Figure Description
[0089] Figure 1 This is a schematic diagram of the structure of the negative electrode material obtained in an embodiment of the present invention.
[0090] The attached figures are labeled as follows:
[0091] 1-Kernel, 2-First overlay, 3-Second overlay, 4-Third overlay. Detailed Implementation
[0092] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.
[0093] The specific information of the raw materials used in the following examples and comparative examples is as follows:
[0094] PAN: Supplier is Sigma-Aldrich, molecular weight is 150,000 Da.
[0095] Example 1
[0096] The negative electrode material of this embodiment is prepared by the following steps:
[0097] S1. Preparation of the first precursor (primary carbon deposition)
[0098] Weigh 1 kg of porous carbon and place it in a fluidized bed. Stir at 50 rpm and purge with nitrogen gas at 5 L / min until the oxygen content is below 100 ppm. Then reduce the nitrogen flow rate to 3 L / min and simultaneously raise the temperature to 550 °C at 5 °C / min. When the temperature reaches 550 °C, increase the nitrogen flow rate to 10 L / min and purge with silane at 2 L / min for 400 min. Then stop silane purge and purge with acetylene at 2 L / min for 40 min. Then turn off acetylene purge and cool down at 2 °C / min until the material is discharged at room temperature to obtain the first precursor.
[0099] The silicon content in the first precursor was determined to be 50.2 wt%. Specifically, this can be determined by the following steps: Weigh 3 g of the first precursor, place it in a muffle furnace at 1200℃ and calcine for 12 hours, then calculate the silicon content based on the mass change (silicon becomes silicon oxide after calcination).
[0100] S2, Preparation of the second precursor
[0101] Prepare 2 kg of the first precursor (silicon content 50.2 wt%) in step S1 and place it in 3 kg of pure water. Stir at 1000 rpm for 2 h to prepare the first mixture for later use. Weigh 40 g of PAN and 20 g of ferric nitrate and place them in 1 kg of pure water. Stir at 2000 rpm for 2 h to prepare the second mixture for later use. Add the second mixture to the first mixture in three equal portions and stir at 800 rpm and 45 °C for 2 h to perform preheating treatment.
[0102] Solid-liquid separation was then carried out by pressure filtration (pressure of 0.1 MPa), and the solid material was then placed in a VC dryer at 120°C for 6 hours to dry, thus obtaining the dried material.
[0103] The dried material was placed in a nitrogen atmosphere at a constant temperature of 280℃ for 6 hours for heat treatment, and then cooled and discharged at a cooling rate of 2℃ / min to obtain the second precursor.
[0104] S3. Preparation of negative electrode material (secondary carbon deposition)
[0105] The second precursor was placed in a fluidized bed, and acetylene was introduced at a flow rate of 5 L / min, while nitrogen was introduced at a flow rate of 15 L / min. Secondary carbon deposition was carried out at a constant temperature of 550 °C for 6 h. Subsequently, the material was washed with water, acid (0.5 mol / L hydrochloric acid), and water, while maintaining a solid-liquid ratio of 1:2. After drying, the final anode material was obtained.
[0106] The structural schematic diagram of the obtained negative electrode material is shown below. Figure 1As shown, the structure specifically includes the following components from the inside out: a core 1, a first coating layer 2, a second coating layer 3, and a third coating layer 4; wherein, the core includes a porous carbon matrix and silicon particles deposited in the pores of the porous carbon matrix, the first coating layer includes amorphous carbon, the second coating layer includes an elastic polymer layer (PAN) and a metal oxide (Fe2O3), and the elastic polymer layer exists in a three-dimensional cyclic structure, the metal oxide is uniformly distributed on the surface of the elastic polymer layer, and the third coating layer includes graphite microcrystals and amorphous carbon, wherein the graphite microcrystals are uniformly distributed in the amorphous carbon.
[0107] The resulting anode material contains 47.6 wt% silicon, 50.4 wt% carbon, 1.5 wt% PAN, and 0.5 wt% Fe2O3.
[0108] The carbon content was tested using a carbon-sulfur analyzer, and the test was conducted in accordance with the national standard GB / T 20123-2006. The silicon content was calculated based on the silicon content and feed amount of the first precursor, while the PAN content and Fe2O3 content were calculated based on the feed amounts of PAN and the metal source.
[0109] Example 2
[0110] Unlike Example 1, in step S2, the amount of PAN used is 20g.
[0111] Example 3
[0112] Unlike Example 1, in step S2, the amount of PAN used is 60g.
[0113] Example 4
[0114] Unlike Example 1, in step S2, the amount of ferric nitrate used is 10g.
[0115] Example 5
[0116] Unlike Example 1, in step S2, the amount of ferric nitrate used is 30g.
[0117] Example 6
[0118] Unlike Example 1, in step S3, the secondary carbon deposition temperature is 450°C.
[0119] Example 7
[0120] Unlike Example 1, in step S3, the secondary carbon deposition temperature is 600°C.
[0121] Example 8
[0122] Unlike Example 1, in step S3, the acetylene gas velocity is 8 L / min.
[0123] Example 9
[0124] Unlike Example 1, in step S3, the acetylene gas velocity is 3 L / min.
[0125] Example 10
[0126] Unlike Example 1, in step S2, PAN is replaced with polyimide.
[0127] Example 11
[0128] Unlike Example 1, in step S2, ferric nitrate is replaced with ferric chloride.
[0129] Example 12
[0130] Unlike Example 1, in step S2, the preheating temperature is 400°C.
[0131] The negative electrode materials obtained in Examples 1-12 can simultaneously satisfy the following:
[0132] The silicon content is 40-60 wt%, the carbon content is 40-60 wt%, the elastic polymer content is 0.1-5 wt%, the metal oxide content is 0.1-10 wt%, the thickness of the first coating layer is 5-15 nm, the thickness of the second coating layer is 1-5 nm, and the thickness of the third coating layer is 5-35 nm.
[0133] Comparative Example 1
[0134] Unlike Example 1, ferric nitrate is not added in step S2.
[0135] Comparative Example 2
[0136] Unlike Example 1, PAN is not added in step S2.
[0137] Comparative Example 3
[0138] Unlike Example 1, step S2 is as follows:
[0139] 2 kg of the first precursor (silicon content 50.2 wt%) was prepared in step S1 and placed in a nitrogen atmosphere at a constant temperature of 280 °C for 6 h for heat treatment. Then, the material was discharged by cooling at a rate of 2 °C / min to obtain the second precursor.
[0140] Effect Example
[0141] The anode materials obtained in Examples 1-12 and Comparative Examples 1-3 were characterized by the following electrochemical performance:
[0142] (1) Battery preparation
[0143] Negative electrode sheet: First, accurately weigh the negative electrode material, Super P conductive additive, and PAA binder prepared in the examples and comparative examples according to a mass ratio of 85:7:8. Place these materials in a deionized water solvent and stir thoroughly for 4 hours using a magnetic stirrer to ensure uniform mixing and form a uniform slurry. Use a transfer coating machine to uniformly coat the prepared slurry onto the Cu current collector. Place the coated current collector in a constant temperature environment of 100°C to dry for 24 hours to ensure that the moisture in the slurry is completely evaporated, thereby enhancing the stability of the electrode. Cut the dried electrode into circular electrode sheets with a diameter of 16 mm to serve as the negative electrode sheet.
[0144] The positive electrode is a lithium electrode;
[0145] The diaphragm is a polypropylene membrane;
[0146] Electrolyte: LiPF6 was dissolved in a mixed solvent of EC and DEC (mass ratio of EC to DEC was 1:1) as the electrolyte.
[0147] In an argon-filled glove box, lithium sheets, separators, negative electrodes, and electrolytes are assembled to obtain a coin cell (model CR2430).
[0148] (2) Electrical performance test
[0149] Test conditions: The assembled button cells were left to stand at room temperature for 12 hours to ensure that the internal components of the cells were in full contact and reached a stable state. The cycle performance and rate performance of the cells were then tested using the Newway BTSDA battery testing system.
[0150] ① Capacity, First-efficacy
[0151] At 25°C, the coin cells assembled using the above method were subjected to charge-discharge tests at a current density of 1C and a voltage range of 0.005-1.5V. The initial discharge capacity and initial charge capacity were recorded, and the first efficiency was calculated using the following formula:
[0152] First-time efficiency = (First charge capacity / First discharge capacity) × 100%.
[0153] ② Cyclic performance
[0154] At 25°C, the coin cells assembled using the above method were subjected to charge-discharge tests at a current density of 1C and a voltage range of 0.005-1.5V for 100 cycles. The initial discharge capacity and the discharge capacity after 100 cycles were recorded and calculated using the following formula:
[0155] 100-cycle capacity retention rate = (100-cycle discharge capacity / first-cycle discharge capacity) × 100%.
[0156] ③ Ratio performance
[0157] The discharge specific capacity of the coin cells assembled by the above method was tested at 25℃ and within a voltage range of 0.005-1.5 V (vs Li / Li+) at 4C, and the 4C rate capability was calculated using the following formula:
[0158] 4C rate ratio = constant current discharge capacity / total discharge capacity × 100%.
[0159] ④ Expansion rate
[0160] The thickness is obtained by direct calculation through battery disassembly and testing or by in-situ expansion testing. Specifically, at 25°C, the coin cells assembled using the above method are charged and discharged within a current density of 1C and a voltage range of 0.005-1.5V. The full lithium insertion thickness and full lithium extraction thickness are recorded, and the expansion rate is calculated using the following formula:
[0161] Expansion rate = (full lithium insertion thickness - full lithium extraction thickness) / coating thickness after electrode rolling × 100%.
[0162] The results are shown in Table 1. The capacity in the table is the initial charge capacity measured under test conditions ① above.
[0163] Table 1
[0164]
[0165] The results show that:
[0166] When the negative electrode materials obtained in Examples 1-12 are used in batteries, they can simultaneously guarantee: the initial charge capacity is not less than 1760mAh / g, the initial efficiency is not less than 90%, the expansion rate is not higher than 70%, the 4C rate ratio is not less than 45%, and the capacity retention rate after 100 cycles is not less than 90%.
[0167] In contrast, when the negative electrode material of Comparative Example 1 does not involve metal oxides, the negative electrode material of Comparative Example 2 does not involve PAN, and the negative electrode material of Comparative Example 3 does not involve PAN-coordination metal layer, the expansion rate of the resulting batteries is significantly increased, and the 4C rate ratio and the capacity retention rate after 100 cycles are significantly reduced.
[0168] In summary, the results show that the anode material of this invention, based on a multilayer structure of "porous carbon / silicon matrix - carbon coating layer - elastic polymer coordination metal layer - carbon coating layer containing graphite microcrystals," effectively suppresses expansion problems during use and simultaneously improves conductivity and lithium conductivity. When used in batteries, it effectively improves the overall performance of the resulting batteries, such as fast charging performance, rate performance, and cycle performance. Furthermore, this preparation method ensures the uniform dispersion of graphite microcrystals and process stability during the coating process. Among these, the elastic polymer coordination metal layer plays the most crucial role; only when this layer structure is present can the formation of polymer cyclization structures and graphite microcrystals be guaranteed, thereby ensuring the simultaneous improvement of the aforementioned multiple performance aspects.
Claims
1. A negative electrode material, characterized by, The negative electrode material comprises the following structures from inside to outside: an inner core, a first coating layer, a second coating layer and a third coating layer; wherein, The inner core comprises a porous carbon matrix and silicon particles deposited in the pore channels of the porous carbon matrix; The first coating layer comprises amorphous carbon; The second coating layer comprises an elastic polymer layer and a metal oxide, and the elastic polymer layer exists in a three-dimensional ring structure, and the metal oxide is uniformly distributed on the surface of the elastic polymer layer; The third coating layer comprises graphite crystallites and amorphous carbon, and the graphite crystallites are uniformly distributed in the amorphous carbon.
2. The negative electrode material of claim 1, wherein, The negative electrode material satisfies one or more of the following conditions: (1) The elastic polymer comprises one or more of polyacrylonitrile, polyaniline, polyvinyl alcohol, polyimide, polyurethane and corresponding derivatives thereof, such as polyacrylonitrile and / or polyimide; (2) In the negative electrode material, the content of the elastic polymer is 0.1-5wt%, for example 1.5wt%; (3) The metal oxide comprises a transition metal oxide, preferably one or more of oxides of Fe, Cu, Co and Ni, such as one or more of ferrous oxide, ferric oxide, magnetite, cuprous oxide, cupric oxide, cobaltous oxide, cobalt oxide, nickelous oxide and nickel oxide; (4) In the negative electrode material, the content of the metal oxide is 0.1wt%-10wt%, for example 0.5wt%.
3. The negative electrode material of claim 1, wherein The negative electrode material satisfies one or more of the following conditions: (1) The silicon content of the negative electrode material is 40wt%-60wt%, for example 47.6wt%; (2) The carbon content of the negative electrode material is 40wt%-60wt%, for example 47.3wt%; (3) The thickness of the first coating layer is 5-15nm; (4) The thickness of the second coating layer is 1-5nm; (5) The thickness of the third coating layer is 5-35nm.
4. A method for producing a negative electrode material, characterized by, The preparation method of the negative electrode material comprises the following steps: S1, the inner core material is subjected to one-time carbon deposition using a first deposition gas to obtain a first precursor; wherein the inner core material comprises a porous carbon matrix and silicon particles deposited in the pore channels of the porous carbon matrix, and the first deposition gas comprises a first carbon source gas; S2, a mixed solution containing the first precursor, a metal source and a polymer is subjected to preheating treatment and heat treatment to obtain a second precursor; wherein the preheating treatment temperature is lower than the heat treatment temperature; S3, the second precursor is subjected to two-time carbon deposition using a second deposition gas to obtain the negative electrode material; wherein the second deposition gas comprises a second carbon source gas.
5. The method of claim 4, wherein the negative electrode material is prepared by the steps of: mixing the carbon material and the lithium metal oxide; and adding the binder to the mixture. The preparation method of the negative electrode material satisfies one or more of the following conditions: (1) In step S1, the first carbon source gas is introduced at a gas speed of 1-5L / min, for example 2L / min, per 1kg of the porous carbon matrix; (2) In step S2, the metal source comprises a transition metal salt; wherein the transition metal salt preferably comprises one or more of Fe salt, Cu salt, Co salt and Ni salt; wherein the transition metal salt preferably comprises one or more of nitrate salt, sulfate salt and chloride salt; (3) In step S2, the mass ratio of the metal source and the first precursor is 0.1%-5%, for example, 0.5%, 1% or 1.5%; (4) In step S2, the polymer includes one or more of polyacrylonitrile, polyaniline, polyvinyl alcohol, polyimide, polyurethane and corresponding derivatives thereof, for example, polyacrylonitrile and / or polyimide; (5) In step S2, the mass ratio of the polymer and the first precursor is 0.1%-10%, for example, 1%, 2% or 3%; (6) In step S2, the temperature of the pre-heating treatment is 40-50℃, for example, 45℃; (7) In step S2, the temperature of the heat treatment is 100-400℃, for example, 250℃ or 280℃; (8) In step S3, the flow rate of the first carbon source gas is 1-10 L / min, for example, 3 L / min, 5 L / min or 8 L / min, based on 2 kg of the first precursor; (9) In step S3, the temperature of the secondary carbon deposition is 200-600℃, for example, 450℃, 550℃ or 600℃.
6. The method of claim 4, wherein the negative electrode material is prepared by the steps of: mixing the carbon material and the lithium metal oxide; and adding the binder to the mixture. The preparation method of the negative electrode material meets one or more of the following conditions: (1) In step S1, the preparation of the core material includes the following steps: The porous carbon matrix is subjected to silicon deposition using a third deposition gas to obtain the core material; wherein the third deposition gas contains a silicon source gas; wherein the silicon source gas is, for example, monosilane; wherein the flow rate of the silicon source gas is preferably 1-5 L / min, for example, 2 L / min, based on 1 kg of the porous carbon matrix; wherein the temperature of the silicon deposition is preferably 500-600℃, for example, 550℃; wherein the time of the silicon deposition is preferably 300-500 min, for example, 400 min; wherein the heating rate before the silicon deposition is preferably 2-10℃ / min, for example, 5℃ / min; (2) In step S1, the first carbon source gas is acetylene; (3) In step S1, the temperature of the primary carbon deposition is 500-600℃, for example, 550℃; (4) In step S1, the time of the primary carbon deposition is 30-50 min, for example, 40 min; (5) In step S1, after the primary carbon deposition, a step of cooling is further included, and the cooling rate of the cooling is preferably 1-5℃ / min, for example, 2℃ / min.
7. The method of claim 4, wherein the negative electrode material is prepared by the steps of: mixing the carbon material, the silicon material, and the binder to form a mixture; and compressing the mixture to form the negative electrode material. The preparation method of the negative electrode material meets one or more of the following conditions: (1) In step S2, the preparation of the mixed solution includes the following steps: Ⅰ, the first precursor and water are mixed to obtain a first mixed solution; Ⅱ, the polymer and the metal source are mixed to obtain a second mixed solution; Ⅲ, the second mixed solution is added to the first mixed solution in batches, and is mixed to obtain the mixed solution; wherein in step III, the addition in batches is preferably in three equal batches; (2) In step S2, the time of the pre-heating treatment is 1-3h, for example, 2h; (3) In step S2, after the pre-heating treatment, a step of solid-liquid separation to obtain the solid, and drying, is further included; (4) In step S2, the time of the heat treatment is 4-8h, for example, 6h; (5) In step S2, the heat treatment is performed under inert conditions; preferably, the inert gas is one or more of nitrogen, argon and helium, for example, nitrogen; (6) In step S2, the heat treatment is followed by a step of cooling; preferably, the cooling rate is 1-5℃ / min, for example, 2℃ / min.
8. The method of claim 4, wherein the negative electrode material is prepared by the steps of: The preparation method of the negative electrode material satisfies one or more of the following conditions: (1) In step S3, the second carbon source gas is acetylene; (2) In step S3, the time for the secondary carbon deposition is 4-8h, for example, 6h; (3) In step S3, the secondary carbon deposition is performed in a fluidized bed; (4) In step S3, the secondary carbon deposition is followed by steps of washing and drying; Preferably, the washing comprises washing with water and acid alternately, for example, washing with water, acid and water in sequence.
9. A negative electrode material, characterized by, The negative electrode material is prepared by the preparation method of the negative electrode material according to any one of claims 4-8.
10. A lithium-ion battery, characterized by, The lithium ion battery comprises the negative electrode material according to any one of claims 1-3 and 9.