Composite lithium battery negative electrode material, preparation method thereof and lithium battery negative electrode

Abstract

This invention provides a composite lithium-ion battery anode material, its preparation method, and a lithium-ion battery anode, belonging to the technical field of battery anode materials. The composite lithium-ion battery anode material provided by this invention comprises a SiOC matrix and Sn atoms doped into the SiOC matrix; the mass of the Sn atoms is 1-10% of the total mass of the composite lithium-ion battery anode material. The microstructure of the composite lithium-ion battery anode material provided by this invention is a cross-linked, multi-level spherical morphology, and EDS surface scan shows that Si, O, C, and Sn elements are uniformly dispersed, with no Sn nanoparticles appearing. When the composite lithium-ion battery anode material provided by this invention is used in a lithium-ion battery, electrochemical performance testing shows an initial coulombic efficiency as high as 88%, and good rate performance and cycle stability. At a current density of 2 A / g, the specific capacity reaches 850 mA / g, and it can stably cycle 1000 times at a current density of 1 A / g.

Description

Technical Field

[0001] This invention relates to the field of battery anode material technology, and in particular to a composite lithium battery anode material, its preparation method, and a lithium battery anode. Background Technology

[0002] Currently, commercial lithium-ion batteries mainly use graphite as the anode, which has a low specific capacity. Its relatively low theoretical capacity cannot meet the demands of electric vehicles and other applications. Silicon anodes exhibit a theoretical specific capacity ten times that of carbon and are considered the most promising high-energy anode material. However, the large volume changes, severe structural collapse, and susceptibility to detachment from the current collector during charging and discharging of silicon anodes are major obstacles to their large-scale application.

[0003] Currently, silicon dioxide anode, i.e., SiO x (0 < x < 2) exhibits relatively small volume change (~200%) and good cycle stability. The reason for this is that SiO₂... x During the initial discharge, it reacts with lithium ions to generate Li. x The mixture consists of Si alloys, Li₂O, and lithium-containing silicates (Li₄SiO₄); the resulting Li₂O and Li₄SiO₄ can act as buffer layers to suppress volume expansion. However, Li₂O and Li₄SiO₄ are irreversible inert substances, which can lead to the formation of SiO₂. x The initial coulombic efficiency of the negative electrode is often below 60%. Initial coulombic efficiency is a crucial indicator in full-cell design, determining the utilization rate of active materials and the total mass of the battery, and is essential for improving the efficiency of SiO2. x The initial coulombic efficiency of the negative electrode is of great significance. However, current technologies lack effective strategies to address this issue in SiO2. x The problem of low initial coulomb efficiency at the negative electrode.

[0004] Therefore, there is an urgent need to provide a composite lithium battery anode material that can achieve a high first-pass coulombic efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a composite lithium battery anode material, its preparation method, and a lithium battery anode. The composite lithium battery anode material provided by this invention has a high initial coulombic efficiency.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a composite lithium battery anode material, which includes a SiOC matrix and Sn atoms doped in the SiOC matrix.

[0008] The mass of the Sn atom is 1 to 10% of the total mass of the composite lithium battery anode material.

[0009] Preferably, the mass of the Sn atom is 2-9% of the total mass of the composite lithium battery anode material.

[0010] Preferably, the composite lithium battery anode material has the morphology of a cross-linked multi-level spherical powder.

[0011] Preferably, the particle size of the composite lithium battery anode material is 100–200 nm.

[0012] The present invention also provides a method for preparing the composite lithium battery anode material described in the above technical solution, comprising the following steps:

[0013] (1) The silane coupling agent and dibutyltin dilaurate are mixed and then subjected to low temperature treatment to obtain a raw material mixture gas;

[0014] (2) The raw material mixture obtained in step (1) is mixed with the carrier fluid and then subjected to high temperature treatment to obtain a composite lithium battery anode material.

[0015] Preferably, the temperature of the low-temperature treatment in step (1) is 200 to 500°C.

[0016] Preferably, the carrier fluid in step (2) is one or both of argon and nitrogen.

[0017] Preferably, the flow rate of the carrier fluid is 50 to 200 sccm.

[0018] Preferably, the high-temperature treatment in step (2) is at a temperature of 800–1300°C and the high-temperature treatment time is 10–20 seconds.

[0019] The present invention also provides a lithium battery anode, which is prepared from the composite lithium battery anode material described in the above technical solution or the composite lithium battery anode material prepared by the preparation method described in the above technical solution.

[0020] This invention provides a composite lithium-ion battery anode material, comprising a SiOC matrix and Sn atoms doped in the SiOC matrix; the mass of the Sn atoms is 1-10% of the total mass of the composite lithium-ion battery anode material. This invention uses SiOC as the matrix, and by substituting O with C, the amount of O introduced can be reduced, thereby effectively suppressing the formation of irreversible inert substances such as Li₂O and Li₄SiO₄. Furthermore, the excellent conductivity of carbon itself can improve the electron transport efficiency of the anode material, thus giving it excellent rate performance and cycle stability. Simultaneously, by doping Sn into SiOC, the large Sn atoms can cause a "local expansion" effect in the transport of Li ions, which is beneficial for lithium ion transport, thereby improving the initial coulombic efficiency.

[0021] The results of the embodiments show that the microstructure of the composite lithium battery anode material provided by the present invention is consistent with the results of TEM and SEM characterization, both showing a cross-linked multi-level spherical morphology. Furthermore, the EDS surface scan structure shows that Si, O, C, and Sn elements are uniformly dispersed, with no Sn nanoparticles appearing. When the composite lithium battery anode material provided by the present invention is used in a lithium-ion battery, electrochemical performance tests are conducted. Its initial coulombic efficiency is as high as 88%, and it has good rate performance and cycle stability. The specific capacity is as high as 850 mA / g at a current density of 2 A / g, and it can stably cycle 1000 times at a current density of 1 A / g. Attached Figure Description

[0022] Figure 1 The image shows the Sn-SiOC composite material provided in Example 1 of this invention at 7000x magnification using a SEM.

[0023] Figure 2 This is a SEM image of the Sn-SiOC composite material provided in Example 1 of the present invention at 20,000x magnification.

[0024] Figure 3 This is a SEM image of the Sn-SiOC composite material provided in Example 1 of the present invention at 60,000x magnification.

[0025] Figure 4 The XRD pattern of the Sn-SiOC composite material provided in Example 1 of this invention;

[0026] Figure 5 This is a TEM image of the Sn-SiOC composite material provided in Example 1 of the present invention;

[0027] Figure 6 for Figure 5 TEM image of a single spherical Sn-SiOC in the image;

[0028] Figure 7 For the present invention Figure 6 A magnified TEM image of a portion of the image;

[0029] Figure 8 This is an EDS image of the Sn-SiOC composite material provided in Example 1 of the present invention; wherein, Figure 8 From left to right, the images show the TEM image of the region used for EDS analysis and the EDS images of Si, O, C, and Sn in that region.

[0030] Figure 9 The rate performance curve of the 2032 button battery prepared in Application Example 1 of this invention;

[0031] Figure 10 The charge-discharge curve of the 2032 button battery prepared in Application Example 1 of the present invention;

[0032] Figure 11 The graph shows the long-cycle performance of the 2032 button battery prepared in Application Example 1 of this invention. Detailed Implementation

[0033] This invention provides a composite lithium battery anode material, comprising a SiOC matrix and Sn atoms doped in the SiOC matrix;

[0034] The mass of the Sn atom is 1 to 10% of the total mass of the composite lithium battery anode material.

[0035] The composite lithium-ion battery anode material provided by this invention includes a SiOC matrix. By using SiOC as the matrix, this invention utilizes C to replace O, thereby reducing the amount of O introduced and effectively suppressing the formation of irreversible inert substances such as Li2O and Li4SiO4. Furthermore, the excellent conductivity of carbon itself improves the electron transport efficiency of the anode material, thus effectively improving the initial coulombic efficiency of the lithium-ion battery and giving it excellent rate performance and cycle stability.

[0036] The composite lithium battery anode material provided by the present invention includes Sn atoms doped in the SiOC matrix.

[0037] In this invention, the mass of the Sn atoms is 1-10% of the total mass of the composite lithium battery anode material, preferably 2-9%, more preferably 3-8%, most preferably 4-7%, and even more preferably 5-6%. By controlling the Sn content within the above range, this invention enables Sn to be doped into SiOC in atomic form.

[0038] In this invention, the composite lithium battery anode material is preferably a cross-linked, multi-level spherical powder. By controlling the morphology of the composite lithium battery anode material to be a cross-linked, multi-level spherical powder, this invention enables it to have high dispersibility, which is more conducive to electron transport when used in lithium-ion batteries, thereby improving the initial coulombic efficiency of lithium-ion batteries and giving them excellent rate performance and cycle stability.

[0039] In this invention, the particle size of the composite lithium battery anode material is preferably 100–200 nm, more preferably 120–180 nm, and most preferably 140–160 nm. By controlling the particle size of the composite lithium battery anode material within the above range, this invention enables it to have a higher specific surface area, which is more conducive to its firm bonding to the current collector, thereby giving the lithium battery anode material high initial coulombic efficiency and excellent rate performance and cycle stability.

[0040] The composite lithium battery anode material provided by this invention has high initial coulombic efficiency, as well as excellent rate performance and cycle stability.

[0041] The present invention also provides a method for preparing the composite lithium battery anode material described in the above technical solution, comprising the following steps:

[0042] (1) The silane coupling agent and dibutyltin dilaurate are mixed and then subjected to low temperature treatment to obtain a raw material mixture gas;

[0043] (2) The raw material mixture obtained in step (1) is mixed with the carrier fluid and then subjected to high temperature treatment to obtain a composite lithium battery anode material.

[0044] This invention involves mixing a silane coupling agent and dibutyltin dilaurate, followed by low-temperature treatment to obtain a raw material mixture gas. By selecting a silane coupling agent and dibutyltin dilaurate as raw materials, the invention utilizes the silane coupling agent to provide both silicon and carbon sources, and the dibutyltin dilaurate to provide a tin source. The two are miscible after mixing. Due to the interaction between the groups of the silane coupling agent and the dibutyltin dilaurate, they aggregate. During low-temperature treatment, the silane coupling agent can vaporize from a liquid state into a gas, while the dibutyltin dilaurate can decompose at low temperatures. The resulting tin-containing substances can bind to the surface of the silane coupling agent. During subsequent high-temperature treatment, the silane coupling agent decomposes into a framework material, allowing Sn to be uniformly doped into the SiOC framework, ultimately forming a cross-linked, multi-level spherical morphology.

[0045] This invention does not impose any particular limitation on the volume ratio of the silane coupling agent to dibutyltin dilaurate, as long as the Sn content in the final composite lithium battery anode material is within the required range. In this invention, the preferred volume ratio of the silane coupling agent to dibutyltin dilaurate is 7:1.

[0046] In this invention, the silane coupling agent is preferably KH560.

[0047] The present invention does not have any particular limitation on the mixing method of the silane coupling agent and dibutyltin dilaurate. Any mixing method known to those skilled in the art that can obtain a uniform mixture is acceptable.

[0048] In this invention, the temperature of the low-temperature treatment is preferably 200–500°C, more preferably 250–450°C, and most preferably 300–400°C. By controlling the temperature of the low-temperature treatment within the above range, this invention enables the silane coupling agent to be fully converted into a gaseous state, and dibutyltin dilaurate to undergo preliminary decomposition.

[0049] The present invention does not have a special limitation on the time of the low-temperature treatment, as long as all raw materials are sufficiently treated at low temperature to form a raw material mixture gas.

[0050] After obtaining the raw material mixture gas, the present invention mixes the raw material mixture gas with a carrier fluid and then performs high-temperature treatment to obtain a composite lithium battery anode material.

[0051] The present invention does not impose any particular limitation on the mixing method of the raw material mixture gas and the carrier fluid. Any mixing method known to those skilled in the art can be used to uniformly mix the raw material mixture gas and the carrier fluid.

[0052] In this invention, the carrier gas is preferably one or both of argon and nitrogen. By selecting these gases as the carrier gas, this invention facilitates the complete carbonization reaction of the raw materials for the composite lithium battery anode material through thorough calcination, while avoiding side reactions with the carrier gas.

[0053] In this invention, the flow rate of the carrier fluid is preferably 50–200 sccm, more preferably 80–180 sccm, and most preferably 100–150 sccm. By controlling the flow rate of the carrier fluid within the above range, this invention enables the raw material mixture to undergo more complete decomposition during high-temperature treatment, thereby forming a composite material with a cross-linked, multi-level spherical morphology.

[0054] In this invention, the temperature of the high-temperature treatment is preferably 800–1300°C, more preferably 900–1200°C, and most preferably 1000–1100°C; the time of the high-temperature treatment is preferably 10–20 seconds, more preferably 12–18 seconds. By controlling the temperature and time of the high-temperature treatment within the above ranges, this invention facilitates the complete decomposition of the raw materials of the composite lithium battery anode material and results in a finer particle size of the formed composite lithium battery anode material.

[0055] The preparation method of the composite lithium battery anode material provided by this invention is more conducive to obtaining cross-linked multi-level spherical composite powder, making it more uniformly dispersed and with a small particle size. This results in the composite lithium battery anode material having high initial coulombic efficiency, as well as excellent rate performance and cycle stability. Moreover, the preparation method is simple, the parameters are easy to control, and the cost is low.

[0056] The present invention also provides a lithium battery anode, which is prepared from the composite lithium battery anode material described in the above technical solution or the composite lithium battery anode material prepared by the preparation method described in the above technical solution.

[0057] This invention does not specifically limit the preparation method of the lithium battery anode; any method well-known to those skilled in the art can be used. In this invention, the preferred preparation method of the lithium battery anode includes the following steps:

[0058] (1) The composite lithium battery anode material is mixed with a conductive agent, a binder and a solvent to obtain a lithium battery anode slurry;

[0059] (2) The lithium battery negative electrode slurry obtained in step (1) is coated on the surface of the current collector and then dried to obtain the lithium battery negative electrode.

[0060] The present invention preferably involves mixing the composite lithium battery anode material with a conductive agent, a binder, and a solvent to obtain a lithium battery anode slurry.

[0061] In this invention, the conductive agent is preferably superP.

[0062] In this invention, the adhesive is preferably polyvinylidene fluoride.

[0063] In this invention, the solvent is preferably N-methylpyrrolidone.

[0064] In this invention, the preferred mass ratio of the composite lithium battery anode material, conductive agent, and binder is 8:1:1.

[0065] The present invention does not have a special limitation on the amount of solvent used; the amount of solvent can be weighed using a method well known to those skilled in the art for preparing lithium battery negative electrode slurry.

[0066] The present invention does not impose any particular limitation on the mixing method of the composite lithium battery negative electrode material with the conductive agent, binder and solvent. Mixing them evenly can be carried out by a mixing method known to those skilled in the art.

[0067] After obtaining the lithium battery negative electrode slurry, the present invention preferably coats the lithium battery negative electrode slurry onto the surface of the current collector and then dries it to obtain the lithium battery negative electrode.

[0068] In this invention, the coating method is preferably scraping.

[0069] In this invention, the current collector is preferably a copper foil.

[0070] In this invention, the drying temperature is preferably 80-100°C; the drying time is preferably 6-12 hours.

[0071] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0072] Example 1

[0073] A composite lithium battery anode material comprises a SiOC matrix and Sn atoms doped in the SiOC matrix, wherein the mass of the Sn atoms is 10% of the total mass of the composite lithium battery anode material; the morphology of the composite lithium battery anode material is a cross-linked multi-level spherical powder with a particle size of 100-200 nm.

[0074] The preparation method of the above-mentioned composite lithium battery anode material specifically includes the following steps:

[0075] (1) The raw materials of the composite lithium battery anode material are mixed and then subjected to low temperature treatment to obtain raw material mixture gas; specifically, silane coupling agent (KH560, 7mL) and dibutyltin dilaurate (1mL) are placed in a furnace at 300℃ for low temperature treatment.

[0076] (2) The raw material mixture obtained in step (1) is mixed with the carrier fluid and then calcined to obtain a composite lithium battery anode material; specifically, argon gas is used as the carrier fluid to mix with the raw material mixture in step (1), and the flow rate of the carrier fluid is controlled to be 200 sccm. The mixture is then fed into a calcining furnace and subjected to high-temperature treatment at 1000℃ for 10s. The composite lithium battery anode material (denoted as Sn-SiOC composite material) is collected at the gas outlet of the calcining furnace.

[0077] The Sn-SiOC composite material provided in Example 1 was characterized using scanning electron microscopy (SEM), and SEM images at different magnifications are shown below. Figures 1-3 As shown, where, Figure 1 The image shows the Sn-SiOC composite material provided in Example 1 at 7000x magnification using a SEM. Figure 2 The image shows the Sn-SiOC composite material provided in Example 1 at 20,000x magnification. Figure 3 The image shows the Sn-SiOC composite material provided in Example 1 at 60,000x magnification.

[0078] according to Figures 1-3 It can be seen that the Sn-SiOC composite material provided in Example 1 has the morphology of cross-linked multi-level spherical powder and a uniformly dispersed structure; at the same time, no particulate matter appears on the surface of the cross-linked multi-level spherical powder, and its surface has a smooth morphology, proving that Sn is uniformly dispersed in the Sn-SiOC composite material in atomic form.

[0079] The Sn-SiOC composite material provided in Example 1 was characterized using an X-ray diffractometer, and the obtained XRD pattern is shown below. Figure 4 As shown.

[0080] Depend on Figure 4 It can be seen that there is only one peak near 25°, and no peak of metallic tin appears, proving that Sn exists in SiOC in atomic form and that the composite material has an amorphous structure.

[0081] The Sn-SiOC composite material provided in Example 1 was characterized using transmission electron microscopy (TEM), and the obtained TEM images are shown below. Figures 5-7 As shown, where Figure 6 for Figure 5 TEM image of a single spherical Sn-SiOC composite material. Figure 7 for Figure 6 A magnified view of a single spherical Sn-SiOC composite material.

[0082] Depend on Figures 5-7 It can be seen that the TEM characterization results are consistent with the SEM characterization results, and no lattice fringes are found under high resolution, further confirming that the microstructure of the Sn-SiOC composite material is a cross-linked multi-level sphere.

[0083] The elemental distribution within the microscopic region of the Sn-SiOC composite material provided in Example 1 was analyzed using a transmission electron microscope (TEM) with its accompanying accessories. The resulting EDS image is shown below. Figure 8 As shown, where Figure 8 From left to right, the images show the TEM image of the region used for EDS analysis and the EDS images of Si, O, C, and Sn.

[0084] according to Figure 8 It can be seen that Si, O, and C in the Sn-SiOC composite material are uniformly distributed in the circular region, that is, the SiOC material composed of Si, O, and C is a spherical framework material, and the Sn element is also uniformly dispersed, but no Sn nanoparticles are present, that is, the Sn element is uniformly dispersed in the SiOC spherical framework material in atomic form.

[0085] Application Example 1

[0086] The Sn-SiOC composite material provided in Example 1 was used to fabricate a lithium battery anode, and its preparation method is as follows:

[0087] The Sn-SiOC composite material provided in Example 1 was mixed with a conductive agent (superP) and a binder (polyvinylidene fluoride, i.e., PVDF) at a mass ratio of 8:1:1. The raw materials were uniformly mixed with NMP as a solvent to obtain a slurry. The slurry was then coated onto a current collector (copper foil) using a scraper. The film was kept at 80°C for 12 hours. After cooling, the electrode was cut into disc electrodes with a diameter of 6 mm for later use.

[0088] The 6mm disc electrode obtained above was assembled with a lithium metal sheet to form a 2032 button cell. Constant current charge-discharge tests were conducted to evaluate its initial coulombic efficiency, rate performance, and cycle stability. The resulting rate curves, charge-discharge curves, and long-cycle curves are shown below. Figure 9 , Figure 10 and Figure 11 As shown.

[0089] according to Figures 9-11 It can be seen that the 2032 button cell has an initial coulombic efficiency of up to 88%; at the same time, it has a specific capacity of up to 850 mA / g at a current density of 2 A / g, and can stably cycle 1000 times at a current density of 1 A / g, showing good rate performance and cycle stability.

[0090] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A composite lithium battery anode material, comprising a SiOC matrix and Sn atoms doped in the SiOC matrix; The mass of the Sn atom is 1-10% of the total mass of the composite lithium battery anode material; The morphology of the composite lithium battery anode material is a cross-linked multi-level spherical powder; The particle size of the composite lithium battery anode material is 100~200nm.

2. The composite lithium battery anode material as described in claim 1, characterized in that, The mass of the Sn atom is 2-9% of the total mass of the composite lithium battery anode material.

3. The method for preparing the composite lithium battery anode material according to any one of claims 1 to 2, comprising the following steps: (1) The silane coupling agent and dibutyltin dilaurate are mixed and then subjected to low temperature treatment to obtain a raw material mixture gas; (2) The raw material mixture obtained in step (1) is mixed with the carrier fluid and then subjected to high temperature treatment to obtain a composite lithium battery anode material.

4. The preparation method according to claim 3, characterized in that, The temperature for low-temperature treatment in step (1) is 200~500℃.

5. The preparation method according to claim 3, characterized in that, The carrier fluid in step (2) is one or both of argon and nitrogen.

6. The preparation method according to claim 3 or 5, characterized in that, The flow rate of the carrier fluid is 50~200 sccm.

7. The preparation method according to claim 3, characterized in that, In step (2), the high temperature treatment temperature is 800~1300℃ and the high temperature treatment time is 10~20s.

8. A lithium battery anode, prepared from the composite lithium battery anode material according to any one of claims 1 to 2 or the composite lithium battery anode material prepared by the preparation method according to any one of claims 3 to 7.

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